Integrated multiple actuator electro-hydraulic units

ABSTRACT

Integrated multiple actuator electro-hydraulic systems as well as their methods of use are described. Depending on the particular application, the integrated electro-hydraulic systems may exhibit different frequency responses and/or may be integrated into a single combined unit.

CROSS REFERENCE OF RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. provisional application Ser. No. 62/387,410, filed Dec. 24,2015, and U.S. provisional application Ser. No. 62/330,619, filed May 2,2016 the disclosures of each of which are incorporated herein byreference in their entirety.

FIELD

The methods and systems described herein relate to integrated multipleactuator electro-hydraulic units.

BACKGROUND

Suspension systems, including active suspension systems, are typicallydesigned to, for example, properly support and orient a vehicle, providesafe handling in various operating environments, and ensure acomfortable ride for occupants. Active suspension systems and theircontrol are described in U.S. Pat. No. 9,260,011 and U.S. patentapplication Ser. No. 14/602,463, filed Jan. 22, 2015 which are herebyincorporated herein by reference in their entirety. Hydraulic actuatorsare also used for adjusting vehicle ride height. For example, ahydraulically actuated spring seat adjustment system may be used forride height adjustment in a vehicle.

SUMMARY

In some embodiments, an active suspension unit for a motor vehicle mayinclude a first active suspension actuator with an internal volume and afirst piston that operates in the internal volume and travels along afirst axis, and applies a force on the body of the vehicle and a wheelassembly of the vehicle. Also included is a second actuator with aninternal volume containing hydraulic fluid and a piston with a secondaxis of travel. The pressure of hydraulic fluid in the second actuatorinduces a force on the piston along the second axis of travel, where thesecond actuator also applies a force on the vehicle body and the samewheel assembly. The active suspension unit includes a first pressuresource that has a port that is in fluid communication with the internalvolume of the first actuator and a second pressure source that has aport that is in fluid communication with the internal volume of thesecond actuator. The two actuators are controlled to cooperatively applya net force on the vehicle body and the wheel assembly. In someembodiments, the first and/or the second pressure sources are hydraulicpumps. In some cases, the first actuator has a faster response than thesecond actuator. A first actuator has a faster response than a secondactuator if it produces a given output more quickly in response to thesame command.

An embodiment of an active suspension unit supporting a corner of avehicle includes a first actuator assembly operatively coupled to anelectric motor. The rotation of the electric motor is at least partiallyconverted to a first linear force that is applied between the vehiclebody and one wheel assembly. The unit also includes a second actuatorassembly that is operatively coupled to at least one electric motor, therotation of which is also converted, at least partially, to a secondlinear force between the vehicle body and the same wheel assembly. Acompliant element is operationally located between the actuator assemblyand the vehicle body or the wheel assembly. The first assembly and thesecond assembly are controlled to cooperatively apply a net force on thevehicle body and wheel assembly. The first assembly has a bandwidthextending to an upper limit of at least 5 Hz, and the second assemblyjointly with the compliant element has a bandwidth of up to, but no morethan, 5 Hz. In some embodiments, the electric motor coupled to the firstassembly and the electric motor coupled to the second assembly are thesame electric motor. A frequency bandwidth of an actuator is the rangeof frequencies over which the output is within at least 3 dB of thecommanded input.

In one embodiment, an integrated motion control unit includes a firstactuator that has a housing with an internal volume separated into acompression volume and an extension volume by a double-acting pistonwhich is attached to a piston rod. In hydraulic actuators with a pistonand a piston rod, the extension volume contracts as the actuator extendsand the piston rod at least partially leaves the actuator housing. Thecompression volume contracts when the actuator is compressed and thepiston rod enters further into the actuator housing.

In this embodiment, the integrated control unit also includes ahydraulic motor-pump that has a first port that is in fluidcommunication with the extension volume and a second port that is influid communication with the compression volume. Further, the integratedmotion control unit includes a second actuator that has a first volume,a second volume, and a double-acting piston that extends radially aroundthe housing of the first actuator and along at least a portion of theaxial length of the housing of the first actuator. In the secondactuator, the first volume is in fluid communication with the first portof the hydraulic motor-pump and the second volume is in fluidcommunication with the second port of the hydraulic motor-pump. Thefirst actuator and the second actuator of the integrated motion controlunit are positioned operatively parallel to each other, and areinterposed between a first structure and a second structure.

External piston actuators may extend radially and encircle thecylindrical housing of an associated actuator which has a piston and apiston rod. Such external piston actuators may also have an extensionvolume and a compression volume. In external piston actuators, theextension volume also contracts as the annular piston moves in theextension direction of the associated actuator and a compression volumethat contracts as the external piston moves in the compression directionof the associated actuator.

In still another embodiment, an integrated motion control unit includesa first actuator that has a housing with an internal volume separatedinto a compression volume and an extension volume by a double-actingpiston with a piston rod attached to it. Additionally, the integratedmotion control unit includes a hydraulic pump (which may be amotor-pump) that has a first port that is in fluid communication withthe extension volume and a second port that is in fluid communicationwith the compression volume, and a pressurized accumulator. Further, theintegrated motion control unit includes a second actuator with asingle-acting piston that extends radially around the housing of thefirst actuator and along at least a portion of the axial length of thehousing of the first actuator. The volume of hydraulic fluid within thesecond actuator separate from the internal volume of the first actuatoris in selective fluid communication with the pressurized accumulator. Amotor-pump, pump-motor, or motor/pump is a hydraulic device that canoperate as a hydraulic pump or as a hydraulic motor.

In yet another embodiment, an integrated motion control unit includes afirst actuator that has a housing with an internal volume separated intoa compression volume and an extension volume by a double-acting piston,and a piston rod attached to the piston. Further, the integrated motioncontrol unit includes a hydraulic pump that has a first port that is influid-communication with the extension volume, and a second port that isin fluid communication with the compression volume. Additionally, theintegrated motion control unit includes a second actuator that includesa first volume, a second volume, and a double-acting piston. Thedouble-acting piston has a first surface that is acted on by the fluidin the first volume, and a second surface that is acted on by the fluidin the second volume. In the second actuator, the first volume is influid communication with the first port of the hydraulic pump, and thesecond volume is in fluid communication with the second port of thehydraulic pump. In the integrated motion control unit, the firstactuator and the second actuator are positioned operatively parallel toeach other, and are interposed between a first and a second structure,where the first actuator has a faster response than the second actuator.Two actuators may be operatively parallel to each other when they exertforces that are effectively in the same or opposed directions.

In another embodiment, a method of controlling relative motion between afirst structure and a second structure by applying a net force on thetwo structure includes: driving a hydraulic pump with an electric motoroperatively coupled to the hydraulic pump; supplying pressurizedhydraulic fluid to a volume in a first actuator, where the firstactuator is interposed between the first and the second structure;supplying pressurized hydraulic fluid to a volume in a second actuator,where the second actuator is interposed between the first and the secondstructures and arranged in an operatively parallel arrangement with thefirst actuator; where a Total Effective Force Area (TEFA) of the firstactuator and the second actuator in at least one of the compressiondirection and the extension direction is a function of the frequency ofpressure variation applied to the first actuator and the second actuatorby the hydraulic pump.

In yet another embodiment, a method of controlling relative motionbetween a first structure and a second structure by applying a net forceon the two structures includes: driving a hydraulic pump with anelectric motor operatively coupled to the hydraulic pump; supplying apressurized fluid to a hydraulic actuation apparatus that is interposedbetween the first and the second structures; where the pressure of thehydraulic fluid acts on the TEFA of the actuation device to produce aforce; and where the TEFA is a function of the frequency of the pressurevariation applied to the hydraulic actuation apparatus by the pump; andapplying the force to the first structure and the second structure.

In another embodiment, an integrated suspension unit includes a firstactuator that includes a housing with an internal cylindrical volumeseparated into a compression volume and an extension volume by adouble-acting piston, and a piston rod attached to the piston. Theintegrated suspension unit also includes a hydraulic motor-pump that hasa first port that is in fluid communication with the extension volume,and a second port that is in fluid communication with the compressionvolume. Additionally, the integrated suspension unit includes a tandemannular double-acting piston that surrounds at least a portion of theaxial length of the housing of the first actuator. The first volume andsecond volume are in fluid communication with the first port of thehydraulic motor-pump, and a third and fourth volume are in fluidcommunication with the second port of the hydraulic motor-pump. Further,the pressure in the first volume acts on the EFA of the first volume andthe pressure in the third volume acts on the EFA of the third volume toproduce a force in the compression direction of the first actuator, thepressure in the second volume acts on the EFA of the second volume, andthe pressure in the fourth volume acts on the EFA of the fourth volumeto produce a force in the compression direction of the first actuator.

In yet another embodiment, an active motion control unit includes afirst actuator with an internal volume and a first piston that isslidably received in the internal volume and travels along a first axis,where the first actuator is interposed between a first structure and asecond structure. Further, the active motion control unit includes asecond actuator with an internal volume containing a hydraulic fluid anda piston with a second axis of travel, where a pressure of the hydraulicfluid induces a force on the piston along the second axis of travel, andwhere the second actuator is interposed between the first structure andthe second structure. The active motion control unit also includes ahydraulic pump with at least a first port that is in fluid communicationwith the internal volume of the first actuator and the internal volumeof the second actuator. Additionally, the active motion control unitincludes a low pass hydraulic filer that regulates fluid flow betweenthe first port and the internal volume in the second actuator, where aresponse frequency of the second actuator is determined, at least inpart, by the low pass filter.

In another embodiment, an active suspension unit of a motor vehicleincludes a first active suspension actuator with an internal volume anda first piston that is slidably received in the internal volume andtravels along a first axis, where the first actuator is interposedbetween a vehicle body and a wheel assembly. Further, the activesuspension unit of a motor vehicle includes a second actuator with aninternal volume containing hydraulic fluid and a piston with a secondaxis of travel, where a pressure of the hydraulic fluid induces a forceon the piston along the second axis of travel. The second actuator isalso interposed between the vehicle body and the wheel assembly. Theactive suspension unit of a motor vehicle further includes a firsthydraulic pump with at least a first port that is in fluid communicationwith the internal volume of the first actuator, and a second hydraulicwith at least a first port that is in fluid communication with theinternal volume of the second actuator. In the active suspension unit ofa motor vehicle, both the first and second actuators are controlled tocooperatively apply a net force on the vehicle body and the wheelassembly.

It should be appreciated that the foregoing concepts, and additionalconcepts discussed below, may be arranged in any suitable combination,as the present disclosure is not limited in this respect. Further, otheradvantages and novel features of the present disclosure will becomeapparent from the following detailed description of various non-limitingembodiments when considered in conjunction with the accompanyingfigures.

In cases where the present specification and a document incorporated byreference include conflicting and/or inconsistent disclosure, thepresent specification shall control. It two or more documentsincorporated by reference include conflicting and/or inconsistentdisclosure respect to each other, then the document having the latereffective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 illustrates a device for characterizing hydraulic low passfilters.

FIG. 2 illustrates a motion control unit with an active suspensionactuator and an auxiliary vehicle ride height adjustment actuatorsupplied by a separate pump.

FIG. 3 illustrates a motion control unit with an active suspensionactuator and an auxiliary vehicle ride height adjustment actuatorpressurized by an accumulator.

FIG. 4 illustrates a motion control unit including three double-actingactuators.

FIG. 5 illustrates a motion control unit including two actuatorssupplied by a single pump where the actuators have different frequencyresponses.

FIG. 6 illustrates another embodiment of a motion control unit withthree actuators operating with different frequency responses.

FIG. 7 illustrates another embodiment of a motion control unit withthree actuators operating with low pass hydraulic filters and a singlepump.

FIG. 8 illustrates an embodiment of a motion control unit with twoactuators operating with different frequency responses supplied by asingle pump.

FIG. 9 illustrates a motion control unit with an active suspensionactuator and a single-acting vehicle height actuator supplied by asingle hydraulic pump.

FIG. 10 illustrates another embodiment of a motion control unit with twoactuators operating with different frequency responses and supplied by asingle pump.

FIG. 11 shows a graph illustrating the power consumption reductionresulting from the use of the motion control unit of FIG. 12.

FIG. 12 illustrates another embodiment of a motion control unit with twoactuators supplied by a single pump.

FIG. 13 illustrates the motion control unit of FIG. 14 where the supplyto one of the actuators is inverted.

FIG. 14 illustrates a motion control unit with an active suspensionactuator, a roll control actuator, and a single acting ride heightactuator.

FIG. 15 illustrates a motion control unit as in FIG. 16 where the supplyto the roll assist actuator is inverted.

FIG. 16 illustrates another embodiment of a motion control unit with anactive suspension actuator, a roll assist actuator, and a height adjustactuator powered by a single pump.

FIG. 17 illustrates a motion control unit with an active suspensionactuator, a ride height adjustment actuator, and an accumulator that ispressurized by using an air compressor.

FIG. 18 illustrates a motion control unit with an active suspensionactuator, a ride height adjustment actuator, and an accumulator that ispressurized by using a hydraulic power take-off unit and pumpcombination.

FIG. 19 illustrates an embodiment of an integrated actuator with anactive suspension actuator and an annular double-acting spring perchactuator.

FIG. 20 illustrates an integrated actuator with an active suspensionactuator and an annular, tandem double-acting spring perch actuator.

FIG. 21 illustrates another embodiment of an integrated actuator with anactive suspension actuator and an annular double-acting spring perchactuator.

FIG. 22 illustrates an embodiment of an integrated actuator with anactive suspension actuator and an annular single-acting spring perchactuator.

FIG. 23 illustrates another embodiment of an integrated actuator with anactive suspension actuator and an annular single-acting spring perchactuator.

FIG. 24 illustrates still another embodiment of an integrated actuatorwith an active suspension actuator and an annular single-acting springperch actuator.

FIG. 25 illustrates yet another embodiment of an integrated actuatorwith an active suspension actuator and an annular single-acting springperch actuator.

FIG. 26 illustrates an embodiment of an integrated actuator with anactive suspension actuator and an annular double-acting spring perchactuator assisted by a pressurized accumulator.

FIG. 27 illustrates another embodiment of an integrated actuator with anactive suspension actuator and an annular double-acting spring perchactuator assisted by a pressurized accumulator.

FIG. 28 illustrates still another embodiment of an integrated actuatorwith an active suspension actuator and an annular double-acting springperch actuator assisted by a pressurized accumulator.

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the system and methods disclosed herein for anactive suspension system. One or more examples of these embodiments areillustrated in the accompanying drawings and described herein. Those ofordinary skill in the art will understand that the systems, methods andexamples described herein and illustrated in the accompanying drawingsare non-limiting exemplary embodiments and that the scope of the presentinvention will be defined solely by the claims.

The features illustrated or described in connection with one exemplaryembodiment may be combined with features of other embodiments and thefeatures may be used individually, singularly and/or in variouscombinations. Such modifications are intended to be included within thescope of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Vehicular suspension systems may use a passive or semi-active damper oractive actuator located in an operatively parallel orientation or in anoperatively series orientation with a primary suspension spring tosupport a vehicle body relative to one of multiple associated wheelassemblies. In some instances, a supplemental single acting actuator,i.e. pressurized fluid is only applied to one side of the associatedpiston, may be used to permit adjustment of a vehicle's ride height. Twoactuators and/or a compliant element and/or a damping element areoperatively in series to each other if the forces that they apply on astructure are effectively in series.

The Inventors have recognized several limitations associated with theabove noted systems. Specifically, many of the systems used for rideheight adjustment use pumps that are sized to support the entire appliedweight of the vehicle. Depending on the particular application, this maylead to the use of large pumps that are expensive and energyinefficient. Accordingly, in some embodiments, the Inventors haverecognized that it may be desirable to provide an overall smallersystem, with reduced energy consumption, active control of ride height,and/or any to address any other applicable desired benefit.

In view of the above, the Inventors have recognized the benefitsassociated with integrated actuator systems, and/or other hydraulicdevices, used to apply forces to two or more associated structures withtwo or more actuators powered with a hydraulic pressure or force source.Additionally or alternatively, multiple pumps and/or pressure sourcesmay be used cooperatively in a manner that reduces the needed total pumpcapacity. Thus, in some embodiments, for example, a combination ofmultiple actuators may be interposed between a wheel assembly and avehicle body, or other structures in operatively parallel and/or seriesarrangements with the one or more suspension springs, to control themotion and/or position of the vehicle body and/or wheels with respect tothe road and/or the relative movement between the structures.Additionally, these hydraulic actuators, dampers, or other hydraulicdevices may be located in operatively parallel and/or seriesarrangements with one or more suspension springs or other deviceslocated within a vehicle or structure in some applications. Further,these systems may be used to control ride height, vehicle roll and/orvehicle motion in the vertical direction by using multiple actuatorspowered by a single hydraulic pump or motor-pump. These systems may alsobe used in applications such as earthquake mitigation systems forbuildings, movement mitigation systems for skyscrapers, and/or any otherappropriate application where actuators may be used for eithergenerating and/or mitigating motion in various frequency ranges and/orapplications as the disclosure is not so limited.

In one embodiment, two or more actuators may be used to control therelative movement of two structures, such as a wheel assembly of avehicle and a vehicle body, at different frequencies. Each of the two ormore actuators may be appropriately sized to work with a pump and/orother pressure source to handle the forces and fluid flows expectedwithin these frequency ranges. Therefore, a first actuator may be sizedto work with a pump and/or other pressure source to efficiently controlthe relative motion between the structures over a broad range offrequencies, while a second actuator may be sized to work with a pumpand/or other pressure source to efficiently control the lower frequencyrelative motion between the structures that is below the frequencythreshold. Without wishing to be bound by theory, higher frequencyrelative motions of structures typically correspond to higher fluid flowvelocities than lower frequency relative motions between the structures.Accordingly, by splitting the frequency response of the suspensionsystem between these two actuators, the overall system may use lessenergy because less fluid needs to be pumped into and out of the lowerfrequency response actuator for handling the movements above thefrequency threshold than would need to be used if a single actuator wereused to mitigate movements of the structures over the entire frequencyrange.

In instances where two or more actuators are used for controlling therelative movement of two associated structures, it may also bebeneficial to control the actuation of these actuators by using a singlepump. In addition, as further described below, in some embodiments, oneor more properly sized hydraulic filters may be used to automaticallycontrol the response of the actuators relative to changes in operationof an associated pressure source such as a pump, hydraulic motor,hydraulic motor/pump and/or a pressurized accumulator. In such anembodiment, a properly sized hydraulic low pass frequency filter may belocated between a pressure source and one or more pressurized fluidchambers in an actuator, such as an extension or compression volume. Alow pass frequency filter may also be referred to as a low pass filter,a hydraulic filter, a frequency filter, a filter, or other similar termin the current disclosure. The frequency filter may exclude componentsof the pressure variations applied by the pressure source from beingapplied to an associated actuator if those components are either above adesired threshold frequency. For example, in one embodiment, one or moreproperly sized hydraulic filters may be located in line between thepressure source and one or more pressurized fluid chambers of anactuator to exclude pressure variations with frequencies above athreshold frequency. Separately, the fluid pressure source may also bein fluid communication with a separate actuator which may allow for thecontrol of the actuator associated with the frequency filter atfrequencies below the threshold frequency and the other actuator atfrequencies above and below the threshold frequency. Of course, aselaborated below, other configurations are also possible as thisdisclosure is not so limited.

In the various embodiments described herein, it should be understoodthat a frequency filter for a hydraulic system may correspond to anyappropriate structure, and/or combination of structures and/or systemattributes, capable of appropriately mitigating pressure variationsabove a desired pressure threshold. This includes structures and systemattributes such as, for example, system compliance, hydraulic mass,fluid mass, fluid path length, valves, restrictions, and/or any otherappropriate structure capable of tuning the frequency response of aparticular flow path between a pressure source and a pressurized volume.One of ordinary skill in the art would be able to determine thefrequency response of a particular flow path using basic hydraulicdesign principles and equations in addition to the use of modelingtechniques such as finite element modeling of the desired hydraulicsystem. Additionally or alternatively, the frequency responsecharacteristics of a hydraulic circuit may be determined experimentallyby, for example, using a high impedance high bandwidth pressure source.Such a source that may be used is a piston pump driven by apiezoelectric stack.

The schematic in FIG. 1 shows an embodiment of high impedance pressuresource 1. The piezo stack actuator 2 moves the piston 3 to producepressure fluctuations at outlet 4. The piezoelectric stack 3 may bebiased in compression by spring 5 and thus allow the piston to be movedwith a bidirectional stroke. Pressure fluctuations in the fluid involume 6, induced by the motion of the piston 3, may be conveyed to thesystem being tested through port 4. The bias spring in FIG. 1 is shownas a coil spring but any convenient spring, such as a stiff BellevilleWasher CDM-602130, may be used. By operating the pressure source over arange of frequencies it is possible to characterize a hydraulic filterin a particular flow channel in order determine the range of frequenciesover which attenuation occurs when using a given hydraulic filter in agiven apparatus.

In addition to the above, the Inventors have recognized the benefitsassociated with the use of an annular double acting piston thatsurrounds at least a portion of the housing of an associated firstactuator. For example, the double acting piston may extend radiallyaround, and along at least a portion of the length, of the firstactuator. The double acting piston may also include a first volume thatis in fluid communication with a first port of an associated pressuresource, such as a hydraulic motor-pump, and a second volume that is influid communication with a second port of the pressure source.Accordingly, the pressure source may apply a differential pressurebetween the two volumes to apply a corresponding force to the annulardouble acting piston in a desired corresponding direction. Depending onthe particular application, the pressure source may also be in fluidcommunication with the first actuator as well. Additionally, the firstactuator and the second actuator may be arranged such that they applyforces operatively parallel to a first structure and a second structurethat they are disposed between. Examples of specific structures relatedto such an embodiment elaborated on further below.

In yet another embodiment, the Inventors have recognized the benefitsassociated with using an accumulator that is in fluid communication withone or more actuators to maintain a desired minimum or nominal pressurethreshold within an extension or compression volume or other pressurizedvolume of one or more actuators within a suspension system. For example,in one embodiment, an accumulator may be in fluid communication with aride height adjustment actuator such that it maintains a pressure in thecompression volume sufficient to support at least a portion of astructure's weight, such as a vehicle's weight. Without wishing to bebound by theory, this may improve the energy efficiency of an actuatordue to an associated pressure source only needing to apply energysufficient to generate a portion of the force, instead of the entireforce, needed to displace the associated structure.

Typically, as a vehicle travels over a road, both the vehicle body andthe wheels may undergo road-induced motion over a wide range offrequencies. For example, the vehicle body may move at frequenciesranging from 0 Hz to 5 Hz, 0 Hz to 4 Hz, 0 Hz to 3 Hz or in any otherappropriate frequency range, including frequencies greater than thosenoted above. Additionally, in some embodiments, the majority ofmovements of a typical vehicle body may occur in a frequency rangebetween about 1 Hz to 3 Hz. In some embodiments, the vehicle bodyfrequencies may be primarily dominated by the resonant frequency of thevehicle body mass supported on the main suspension springs. In additionto the above, in some embodiments, the wheels may move at frequenciesbetween 8 Hz and 20 Hz, 8 Hz and 15 Hz, or in some embodiments atfrequencies of 20 Hz or higher. Wheel movement frequency is oftentimesdominated by the resonant frequency of the unsprung mass supported onthe stiffness of the tire. Of course, one of ordinary skill in the artwould understand that the particular frequencies associated with vehiclebody and wheel movements will vary based on the particular type ofvehicle being used. For example, the suspension responses of a typicalpassenger vehicle are expected be different from those for a large pieceof mining equipment such as dunp truck. Therefore, wheel and bodyfrequencies, as well as response frequencies for other structures, bothgreater and less than those noted above may be used with the variousembodiments disclosed herein as the disclosure is not so limited.

In addition to mitigating vehicle body and/or wheel motion as notedabove, in some embodiments, it may be desirable to mitigate othervarious types of vehicle events such as roll or pitch motion caused bynavigating a turn, accelerating, and/or decelerating. For example, whena vehicle travels along a curved road, the vehicle rolls so that theside of the vehicle closer to the center of rotation is raised while theopposite side of the vehicle moves closer to the road. Similarly, thevehicle may pitch when brakes are applied and the vehicle undergoesvertical movement such that the front of the vehicle typically dips downrelative to the rear of the vehicle, respectively. A correspondingvehicle movement may occur to pitch the front of the vehicle up relativeto the rear of the vehicle during acceleration. These motions may bemitigated in frequency ranges either within the same, or different,frequency ranges than those noted above for body motion frequencies. Insome embodiments, other events such as raising or lowering the vehiclemay be controlled at still another or lower frequency. Accordingly, insome embodiments, the above noted motions may be mitigated atfrequencies between or equal to 0 Hz and 10 Hz, 0 Hz and 5 Hz, 0 Hz and4 Hz, 0 Hz and 2 Hz, 1 Hz and 3 Hz, or any other appropriate frequencyrange including frequencies both greater than and less than those rangesnoted above, as the disclosure is not so limited.

As noted previously, in some embodiments, it may be desirable to alterthe ride height of a vehicle to improve vehicle performance whenencountering different driving conditions and scenarios. For example, itmay be desirable to raise the vehicle body so the vehicle may traversethe transition between a street and an adjoining steep driveway. Atother times, it may be desirable to lower the vehicle when traveling athigh speeds in order to reduce aerodynamic drag forces. Vehicle rideheight may also be altered to compensate for variation in gross vehicleweight. Controlling vehicle ride height may occur at frequencies thatare significantly lower than that of vehicle body frequencies. Forexample in some embodiments, ride height may be controlled atfrequencies between or equal to 0 Hz and 1 Hz, 0 Hz and 0.1 Hz, 0 Hz and0.01 Hz, or any other appropriate frequency including frequencies bothgreater and less than those in the ranges noted above.

In some embodiments, a fast response active suspension actuator may belocated at each corner of a vehicle, and may be used to mitigate motionof the vehicle body and the wheels over a broad spectrum of frequencies.Depending on the particular application, in one embodiment, a fastresponse active suspension actuator may be defined as an actuator thathas a force control frequency bandwidth (i.e. the actuator is capable ofgenerating or resisting forces at frequencies at or below the notedfrequency), extending to at least 30 Hz, 20 Hz, 10 Hz, 5 Hz or any otherappropriate frequency range based on the intended application.

Therefore, it should be understood that in other embodiments, a fastresponse actuator may operate within different operational frequencybandwidths. In some embodiments, a fast response actuator may simplyrefer to an actuator with a frequency response capability that is fasterthan the frequency response capability of an associated second actuator.

In view of the above, in one exemplary embodiment, a fast responseactuator may be interposed between a first structure and a secondstructure such as a top mount and a wheel assembly of a vehicle. Thisfast response actuator may be located operatively in parallel with anauxiliary slower response actuator and/or a suspension spring perchadjustment actuator which may be installed operatively in series with,for example, a coil spring, an air spring, or other convenientsuspension spring device. The spring device may be installed above orbelow the associated actuator as the disclosure is not so limited.

In some vehicular embodiments, the above noted embodiments usingmultiple actuators may be employed at each corner of a vehicle or atother points of other appropriate structures. Regardless, in someinstances, the disclosed combination of multiple actuators and methodsof use described herein may provide a desirable balance of fastresponse, greater force, and/or reduced power consumption than ispossible with a single actuator sized to provide certain combinedperformance of the multiple actuators. In some embodiments, two or moreof these actuators may be combined in a single unit and/or be powered bya single electric motor-generator/hydraulic motor-pump unit.

For the sake of clarity, the embodiments described below in regards tothe figures are described relative to an electric motor. However, itshould be understood that the embodiments described herein may also beoperated using an electric generator and/or an electric motor-generator,where an electric motor-generator is an electrical device that may beoperated as an electric motor and/or an electric generator. Therefore,the embodiments described her may be used with any of the above notedelectrical devices as the disclosure is not so limited.

For the sake of clarity, the embodiments described below in regards tothe figures are also primarily directed to the use of hydraulicmotor-pumps. However, the embodiments described herein are also usablewhere appropriate with hydraulic motors and/or hydraulic pumps. Ahydraulic motor-pump is a hydraulic device that may be operated as ahydraulic motor and/or a hydraulic pump. Accordingly, the embodimentsdescribed herein may be used with any of the above-noted hydraulicdevices as the disclosure is not so limited.

In the embodiments described herein, a spring, such as a main suspensionspring, may be, for example, a coil spring, an air spring or any otherappropriate compliant spring like component or device that may supportthe weight of a vehicle body, or other structure, under staticconditions.

In some embodiments, a higher force but slower response, auxiliaryactive suspension actuator may be used to introduce, mitigate, and/oreliminate certain motions between two associated structures such as rolland/or pitch or assist the faster response actuator in responding toslowly changing forces. When implemented in a vehicle, such anembodiment may include an actuator placed operatively in a seriesarrangement with the main suspension spring which is operatively inparallel with the faster response actuator. By using such anarrangement, the force capacity of the overall system may be increasedwithout significantly increasing the inertance of the system (at higherfrequencies. Again, this combination of actuators may be used to achievea desired level of force without adversely affecting the response of thesystem. For example, in an active suspension system, the pump and fasterresponse actuator are capable of responding quickly to road inputs togenerate corresponding active and/or passive forces so that, forexample, the suspension still appears soft when a high frequency impactis experienced from the road.

In some embodiments of actuation systems, the moment of inertia of therotating elements of the actuator, when the actuator is back-driven byexternal input, is an important parameter. The lower the inertia, themore easily (without producing excessive reaction force) the actuatormay be driven backwards by an external stimulus.

In an actuator with a linear output driven by a rotating device, such asan electric motor, the moment of inertia of all rotating components thatplay a part in converting the output of the motor to the linear outputof the actuator affect the back driveability of the actuator. Theinertia of these components affects the reaction force of the actuatorto an external stimulus. This force is proportional to the sum of themoment of inertia of each rotating part multiplied by its angularacceleration scaled by the square of the motion ratio of angular motionof each component to the linear motion of the actuator output. Themagnitude of this effect is inertance and has the units of kilograms.

In an embodiment of a linear actuator, an electric motor may be coupled,for example, to a pump or a screw mechanism, and/or to a linear lever,through a shaft, which may be held in place, for example, by one or morebearing elements. The rotating parts of each of these elements maycontribute to the system inertance as scaled by their respective motionratios.

For example, bearing elements typically circulate at a fraction of therotational speed of the inner or outer race moving with the elementconstrained by the bearing.

In other embodiments, the inertance may be due, for example, to therotational inertia of a pinion element rotating on a geared rack, or ofa rotating hydraulic pump element and motor in an electro-hydraulicactive suspension actuator.

In some applications, a typical active actuator located operatively inparallel with a suspension spring may be able to achieve a maximum forceexertion of 500 N with an associated pump element contributing 5 kg ofreflected pump inertia to the movement of the vehicle wheel. To generatea maximum force exertion of 1000 N (double the previous), the samesystem may contribute 25 kg of reflected pump inertia to the movement ofthe vehicle wheel assembly. Without active control systems or othermitigating methods, the increased reflected pump inertia would allowhigh frequency road inputs (i.e. those inputs with frequencies above thecontrol bandwidth of the active suspension) to be transmitted to thebody of the car. Accordingly, these systems may not be able to achieve adesired level of road isolation.

In contrast to the above noted higher inertia system, if a slowerresponse actuator operatively in series with a spring element was placedoperatively in parallel with the active suspension system, it couldprovide the additional 500 N of force needed at lower frequencies (forexample between 1 to 3 Hz, or other appropriate frequencies) withoutadding to the reflected pump inertia for high frequency road inputs. Theresult is a system that is able to achieve both high force output andbetter road isolation. While specific forces and system inertias havebeen noted above, it should be understood that the values above havebeen provided for exemplary purposes, and the actuators and otherhydraulic devices described herein may have any appropriate forcecapacity, inertia, and/or frequency response as the disclosure is not solimited.

In some embodiments, an additional actuator may be used to, for example,move a spring perch of a vehicle's main suspension spring in order toadjust a vehicle's ride height and/or to alter the load transmittedthrough the main suspension spring (compressing to increase force on thebody, and extension to reduce the load on the vehicle body). Thisactuator may also be arranged in a series arrangement with the mainsuspension spring. In some embodiments, this actuator, or otherappropriate actuators, may be biased using a pressurized accumulator,such that the actuator is able to support the static weight of a vehiclebody at one corner of the vehicle or other appropriate structure.

In some embodiments, each corner of a vehicle may have, for example, afast response active suspension actuator, an auxiliary high forceactuator, and/or a high force perch adjustment actuator. Alternatively,each corner may have any two of these actuators or only one activeactuator. The actuators in each corner may also work cooperatively witheach other in some embodiments. Additionally, in at least someembodiments, one or more of the actuators in each corner of a vehiclemay work cooperatively with one or more actuators located at othercorners of a vehicle to control the motion of the vehicle.

In certain embodiments, an actuator may be a component or apparatus thatmay be used to apply a desired force to a structure in order, forexample, to move it relative to the ground or relative to a secondstructure. In some embodiments, a linear hydraulic actuator includes asingle or a double-acting hydraulic cylinder with a piston that isslidably received in the cylinder and a piston rod that is attached tothe piston on one side. In some embodiments, a hydraulic pump,operatively coupled to an electric motor, may be used to drive the pumpto supply hydraulic fluid to the hydraulic cylinder in order to applypressure on at least one side (i.e. face) of the piston. This appliedpressure may result in a force along the axis of the piston rod that isproportional to the Effective Force Area (EFA). Typically, the EFA onthe side of the piston attached to the piston rod is the annular areathat is equal to the difference in the cross-sectional area of thepiston and the piston rod. On the opposite side of the piston, the EFAis typically the cross-sectional area of the piston.

When multiple actuators are interposed between two structures andpositioned operatively in a parallel orientation to each other, theTotal EFA (TEFA) in an extension or compression direction may be the sumof the EFA of all the actuators. However, if there is a low pass filterbetween, for example, the compression volume and/or the extension volumeof an actuator and an associated pump, the EFA of the actuator in thecompression and/or the extension directions may be a function of thefrequency of the pump output.

External pistons that encircle the housing of a linear actuator alsohave an EFA in the compression and/or the extension directionscorresponding to the effective surface areas oriented perpendicular tothe axis of the external piston exposed to the pressurized fluid.

If a low pass filter is situated between a pump and an actuator, theactuator may be less responsive at higher frequencies. Therefore, thepresence of a low pass filter may have the effect of reducing the TEFAof one or more actuators for a pump output pressure variations atfrequencies above a threshold frequency of the low pass filter.

For the purposes of clarity, the embodiments described herein areprimarily directed to the use of suspension systems with multipleactuators for controlling the movement of a vehicle body relative to theassociated wheels of the vehicle. However, it should be understood thatthe embodiments described herein referencing the connection of anactuator suspension system to portions of a vehicle may be interpretedgenerally as positioning an actuator, a suspension system, a damper, orany other appropriate hydraulic system between any appropriatecorresponding structures as the disclosure is not limited to uses invehicles.

Turning now to the figures, several non-limiting embodiments aredescribed in further detail. However, it should be understood that thevarious arrangements of components, features, and methods describedrelative to the various embodiments may either be used singularly and/orin any desired combination as the disclosure is not limited to anyparticular embodiment or combination of embodiments.

FIG. 2 illustrates an embodiment of a motion control unit 50 that may beused to control the relative motion of two structures. In the depictedembodiment, the motion control unit includes a first actuatorcorresponding to an active suspension actuator 52 and a second actuatorcorresponding to a spring perch (or ride height adjustment) actuator 53.The motion control unit 50 is interposed between, and connected to, avehicle body 54 and wheel assembly 55. Active suspension actuator 52 isarranged operatively in parallel between the vehicle body and wheelassembly with a series combination of the actuator 53 and a suspensionspring 68 also disposed between the vehicle body and wheel assembly. Thespring is supported relative to the spring perch actuator by anassociated spring perch 68 a.

In the depicted embodiment, the active suspension actuator 52 includes apiston 57 that is slidably received in an interior volume of theactuator cylinder 56, and piston rod 58 attached to the piston at afirst end. The spring perch 68 a is attached to a rod 65 a of the springperch actuator 53 and supports the suspension spring 68. Although inFIG. 4, spring 68 is shown as a coil spring, any appropriate compliantspring like component or device such as, for example, an air spring, maybe used as the disclosure is not so limited. In FIG. 2, the twoactuators are shown as distinct actuators. However, embodiments in whichthe actuators are integrated with one another are also contemplated asdescribed further below and the disclosure is not so limited.

The interior volume of the actuator cylinder 56 is separated by piston57 into a compression volume 59 and extension volume 60 located onopposing sides of the piston. The hydraulic motor-pump 61 is in fluidcommunication with the compression and extension volumes. Accumulator 62may be sized to at least accept fluid volume displaced by rod 58 as itenters the extension volume during a compression stroke and any increasein the volume of hydraulic fluid as a result of thermal expansion. Whilea hydraulic motor-pump has been depicted, as noted previously either ahydraulic pump may also be used.

As discussed above, the integrated suspension unit 50 also includes asecond actuator 53 such as a spring perch or spring seat. Depending onthe embodiment, the second actuator may be a single-sided hydrauliccylinder 63 with hydraulic fluid contained in a compression volume 64within the cylinder. A piston 65 is slidably received in the interiorvolume of the cylinder 63. Hydraulic pump 66 may be used to pump fluidfrom reservoir 67 into the compression volume 64 in order to raisespring 68 which correspondingly raises the vehicle body 54.Alternatively, pump 66 may be used to pump fluid out of compressionvolume 64 in order to lower vehicle body 54. Alternatively oradditionally, fluid may be allowed to drain from volume 64 to reservoir67 by means of an alternate flow path (not shown) that bypasses pump 66.It is noted that, in some embodiments, pump 66 may be replaced by ahydraulic motor/pump as the disclosure is not so limited. In this case,the motor-pump may be used to recover energy when the vehicle islowered.

In some embodiments, valve 69 may be located along the flow path betweenthe reservoir 67 and compression volume 64. Depending on theapplication, the valve may either be, for example, a variable valve or asimple on/off valve. In any case, on the embodiment, the valve may beused to hydraulically lock piston 65 in place in order to keep vehicle54 in an elevated position such as, for example, when pump 66 is turnedoff. Thus, the piston may be hydraulically locked by sealing thecompression volume by closing valve 69.

During operation, an active suspension actuator 52 may be used tocontrol the relative motion between the vehicle body 54 and wheelassembly 55. The active suspension actuator may also be used to apply acontrolled active force (i.e. a force in the direction of motion of thepiston 57, relative to the housing of actuator 56) to induce relativemotion between the vehicle body 54 and the wheel assembly 55.

As detailed above, active suspension actuator 52 may be operated tocontrol the relative motion between the vehicle body 54 and the wheelassembly 55. Further, the spring perch actuator 53 may be used to adjustthe neutral position of the vehicle and the associated wheel assembly.For example, when the hydraulic motor-pump 66 is turned off, the springperch actuator may maintain the vehicle body at a predetermined neutralposition relative to the wheel assembly. This may be accomplished byeither applying an appropriate pressure to the compression volume 64,and/or the valve 69 may be locked, in order to maintain the piston at adesired location and the vehicle in the desired neutral position. Insome vehicle embodiments, multiple motion control units shown in FIG. 2,may be located at various corners of the vehicle and operated incoordination or individually to move the vehicle body vertically and/ortilt or roll the vehicle body.

In the embodiment in FIG. 2, hydraulic motor-pump 61 and pump 66 may beused synergistically to control movement of the vehicle body 54 relativeto the wheel assembly 55. For example, the two actuators may be sizedsuch that they are operated together to raise the vehicle. In such anembodiment, actuator 53 may be sized such work together to lift vehiclebody 54. Such a configuration would obviate the need for pump 66 to havesufficient capacity to provide the necessary pressure so that theactuator 53 may support the applied weight of the vehicle.

In some embodiments, a vehicle may have four wheel assemblies supportinga vehicle body, but the disclosure is not so limited. For example,vehicles with additional or fewer wheel assemblies are alsocontemplated. Further, an integrated suspension unit, such as thosedescribed herein, may be interposed between a vehicle body and one ormore wheel assemblies, and in some embodiments, each wheel assembly andthe vehicle body. Accordingly, in some embodiments, the activesuspension system of a vehicle may include four integrated suspensionunits at the four corners of the vehicle which may be operated incoordination to move the body in unison upward, tilt or pitch the body,or even lift the car with different and/or varying forces.

Similar to the prior embodiment, FIG. 3 illustrates another embodimentof an integrated motion control unit 70 with an active suspensionactuator 52 and spring perch actuator 65. The spring perch actuatorpiston rod 65 a is attached to spring perch 68 a, which supports spring68. However, in this embodiment, compression volume 64 of the springperch actuator is biased to a predetermined pre-charge by an accumulator71 that is in fluid communication with the compression volume 64. Thepressure of the accumulator, and corresponding size of the piston, maybe selected such that the actuator 65 is capable of supporting thefraction of the weight of a vehicle 54 the actuator is associated with.Though pressures, and/or piston sizes, that support either a larger orsmaller weight are also contemplated. Accumulator 71 may be partiallyfilled with gas 71 a which is separated from the corresponding hydraulicfluid 71 b by means of, for example, a diaphragm 71 c. Alternatively, apiston (not shown) may be used instead of, or in addition to, thediaphragm to separate the pressurized gas from the hydraulic fluid. Avalve 72 located on an exterior of the accumulator may be used to addgas or remove gas from the accumulator internal gas volume.

A flow control device 73 may be used to regulate the exchange ofhydraulic fluid between the compression volume 64 and the accumulator71. The flow control device may be, for example, any appropriatelycontrollable valve, such as an electrically or hydraulically actuatedvalve. Alternatively or additionally, an on/off valve may be used, suchas for example, a solenoid valve (not shown). Additionally, oralternatively, a flow restriction or multi-position valve may be used. Amulti-position valve may include check valves, restrictions, or otherflow control devices. During operation of the embodiment in FIG. 5, thevehicle 54 may be lowered by opening flow control device 73 so hydraulicfluid may flow between compression volume 64 and volume 71 b. Ininstances where the pressure in the accumulator and piston aresufficient to support the vehicle, when lowering the vehicle 54, thehydraulic motor-pump 61 may be used to increase pressure in theextension volume 60 and reduce pressure in the compression volume 59.The force resulting from the weight of the vehicle in conjunction withthe differential pressure across piston 57 will overcome the forceapplied on piston 65 by the fluid in compression volume 64 supportingthe vehicle. The resulting net force causes the vehicle to move down,thus forcing fluid out of the compression volume 64. Alternatively, inanother mode of operation when it is desired to raise the vehicle, whileflow control valve 73 is open, the hydraulic motor-pump 61 may beoperated to reduce the pressure in the extension volume 60 relative tothe pressure in the compression volume 59. In this case, the forceresulting from differential pressure across piston 57 in conjunctionwith the force due to the pressure in compression volume 64 may be usedto raise the vehicle, i.e. increase the vehicle ride-height.

As noted above, in some embodiments, the pressure in accumulator 71 andsize of piston 65 may be selected so that the force applied on piston 65due to the pressure in compression volume 64, when flow control device73 is open and hydraulic motor-pump 61 is not being driven, issufficient to support the force resulting from the weight of the car. Itshould be understood that the weight of the car may be supported by oneor more integrated suspension units, such as the suspension unit 70 inFIG. 3. In such an embodiment, the integrated suspension unit wouldsupport a corresponding portion of the vehicle weight. It is noted thatwhen pump 61 is turned off, the pressures in volumes 59 and 60 willeventually equilibrate. However, there will be a net force in the upwarddirection due to the difference in piston area exposed to the pressurein volumes in volumes 59 and 60 (i.e. the difference in the EFA in theextension and compression directions).

FIG. 4 illustrates an embodiment of an integrated motion control unit 80that includes a first actuator 82, a second actuator 83, and a thirdactuator 84. These actuators are interposed between a first structure 85and a second structure 86. The actuators may be used to actively and/orpassively control the relative motion, between the two structures. Insome embodiments, these actuators may be operated in different frequencyranges. These frequency ranges may either be separate from one another,or they may include overlapping frequency ranges, as the disclosure isnot so limited. Each actuator may be connected to the opposingstructures by one or more connecting devices 87 a-87 c and 88 a-88 cthat may be located on opposing sides of the actuators. In someembodiments, one or more of the connecting devices may be, or at leastinclude, a spring and/or a damper. In some embodiments, one or more ofthe connecting devices may be, or at least include, a rigid linkage.

As elaborated on further below, in some embodiments, the three actuatorsdepicted in FIG. 4 may be, directly or indirectly, driven by a singlepump. This pump may also be operated in combination with one or more gaspressurized accumulators. Although three actuators are shown in FIG. 4,any number of actuators may be used including two actuators or more thanthree actuators may be used, as the disclosure is not so limited.

In the embodiment in FIG. 4, each actuator has a compression volume andan extension volume that contains hydraulic fluid whose pressure iscontrolled, either directly or indirectly, by a hydraulic pump. Theextension volumes of actuators 82, 83, and 84 are 82 a, 83 a, and 84 arespectively, while the compression volumes are 82 b, 83 b, and 83 brespectively. In the embodiment in FIG. 4, the pump 89 may be used todirectly control the pressure in either or both of the compression andextension volumes in at least actuator 82 and actuator 83 by supplyinghydraulic fluid to one or both of the compression and extension volumesin actuator 82 and actuator 83. In some embodiments, the pump may alsobe used to supply pressure to the extension and compression volumes ofactuator 84 as well, though embodiments in which a separate pressuresource is used are also contemplated. As depicted in the figure, a lowpass hydraulic filter 90 may be located in the flow path between thepump and compression and/or extension volumes of one or both of actuator82 and actuator 83. The filters may either be located on a single flowpath associated with either one, or both, of the extension orcompression volumes of an actuator. Further, the filters may be used tocontrol the frequency response of the actuators relative to changes inthe pressure applied to the flow paths by the pump. For example, the oneor more filters may be configured such that the first actuator 82responds more slowly to pressure changes applied by the pump than thesecond actuator 83 (i.e. the hydraulic filters associated with the firstactuator may have a lower operational frequency threshold than thesecond actuator).

In some embodiments, one or more of the compression and extensionvolumes in the third actuator 84 may be supplied directly by the pump 89and/or by a pressurized accumulator 91. A low-pass hydraulic filter mayalso be used to affect the frequency response of actuator 84. Dependingon the particular application of each of the above noted actuators, aswell as the actuators described below, are intended for, the low passhydraulic filters may be tuned to a particular frequency threshold. Forexample, a filter may be tuned to permit operation of an actuator atfrequencies corresponding to the various types of events describedpreviously. These events include, but are not limited to: a wheel eventor motion frequency; a body event or motion frequency; vehicle movementfrequencies corresponding to maneuvers such as turns, accelerations, anddecelerations; ride height adjustment frequencies; and other appropriatemovement threshold frequencies.

FIG. 5 illustrates an embodiment of a motion control unit 100 interposedbetween two structures 101 and 102 that may be moved relative to eachother. The motion control unit includes actuator 103, with compressionvolume 103 a and extension volume 103 b, and actuator 104 withcompression volume 104 a and extension volume 104 b. A hydraulic pump105 may be used to supply hydraulic fluid to at least volumes 103 a and104 a. In the depicted embodiment, both actuators may be rigidlyconnected to structure 101. The piston rod 103 c may be rigidlyconnected to structure 102, Alternatively there may be a compliantdevice such as a suspension system top mount (not shown). A piston rod104 c is connected to structure 102 by means of connection device 107,which in this embodiment is a spring. A hydraulic flow control device106 may be used to alter the frequency response of actuator 104 tochanges in pressure caused by pump 105. This flow control device may be,for example, an electronically controlled valve, a passive check-valve,or a multi-position valve as described above. This flow control devicemay also act, in conjunction with the flow channel, and/or otherhydraulic components, to form a hydraulic low pass filter, regulatingthe change in pressure of chamber 104 a with respect to the pressurecaused by pump 105 similar to the embodiments described above. It isnoted that the dashed flow paths in FIG. 5 are flow paths that may flowto other devices such as accumulators and/or may be connected to eachother depending on the particular embodiment.

In some embodiments, in order to achieve a particular frequency responseof actuator 104, a walled orifice restriction may be used as a flowcontrol device 106. This thin-walled orifice restriction may be designedas follows:

The force exerted by actuator 103 may be determined by a pressure inchamber 103 a, P_(103a), and the piston area, A_(103d), indicated as 103d in FIG. 5. The force exerted by actuator 104 may be determined byeither the pressure in chamber 104 a, P 104 a, acting on the pistonarea, A_(104d), labeled as 104 d, or the compression of the seriesspring 107. Since these two elements are in series, they exert the samelinear force as described in Eq. 1 below,

F ₁₀₄ =P _(104a) A _(104d) =K ₁₀₇(x _(104d) −x ₁₀₂)   (Eq. 1)

where F₁₀₄, is the force from actuator 104, K₁₀₇, is the stiffness ofspring element 107, and x_(104d) and x₁₀₂ are the positions of actuatorpiston 104 d and body element 102. Taking the first derivative ofequation 1 shows that for actuator 104 the rate of change in force maybe associated with a flow rate, Q₁₀₆, across a hydraulic flow controldevice 106.

$\begin{matrix}{\frac{{dF}_{104}}{dt} = {{K_{107}\frac{d\left( {x_{104\; d} - x_{102}} \right)}{dt}} = {K_{107}\frac{Q_{106}}{A_{104d}}}}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

A typical thin-wall orifice restriction has flow characteristics thatmay be related to a difference in pressure across the feature. Eq. 3describes the fluid flow rate across an orifice element that may be usedas a hydraulic flow control device 106. Here, ρ, is the density of thefluid, A_(orifice) is the area of the flow restriction, and C is thedischarge coefficient for a particular orifice geometry which may bedetermined empirically.

$\begin{matrix}{Q_{106} = {{CA}_{orifice}\sqrt{\frac{2\left( {P_{104\; a} - P_{105a}} \right)}{\rho}}}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

The two actuators 103 and 104 may respond to a pressure created by pump105 in different ways due to the hydraulic flow control device 106,which as noted above may be a flow restriction. Equations 4 and 5 show achange in force response per unit time for actuator 103 and actuator 104to pressure changes caused by the pump. The response of actuator 103 maybe directly controlled by the pressure change in the pump (whileneglecting line-losses in the connection between 105 and 103 a).However, the force response of actuator 104 may be restricted based onthe parameters of the orifice used as an example of a flow controldevice.

$\begin{matrix}{\frac{{dF}_{103}}{dt} = {\frac{{dP}_{105a}}{dt}A_{103d}}} & \left( {{Eq}.\mspace{14mu} 4} \right) \\{\frac{{dF}_{104}}{dt} = {\frac{K_{107}{CA}_{orifice}}{A_{104d}}\sqrt{\frac{2\left( {P_{104a} - P_{105a}} \right)}{\rho}}}} & \left( {{Eq}.\mspace{14mu} 5} \right)\end{matrix}$

Equation 5 shows that the response rate of actuator 104 may becontrolled using the parameters associated with the flow control deviceas well as the series spring element 107. Additional consideration forthe mass associated with the fluid in the flow path may be taken intoaccount in the model. However, in some applications, an effect of thismay be readily determined experimentally or through computational fluiddynamic simulations of the fluid system instead.

FIG. 6 illustrates an embodiment of a motion control unit 110 thatincludes three actuators 111, 112, and 113. The three actuators may becoordinated to control the relative motion between first and secondstructures 114 and 115. In this embodiment, actuators 112 and 113 areganged together by first and second intermediate structures 114 a and115 a. Connecting devices, 116 a and 116 b may be used to connectactuator 111 to the first and second structures 114 and 115respectively. Connecting devices 116 c and 116 d may be used to connectthe first structure and first intermediate structure 114 and 114 a, andthe second structure and second intermediate structure 115 and 115 arespectively. In some embodiments, a connecting device 116 e may be usedto connect the piston rod of actuator 113 to the second intermediatestructure 115 a and the opposing end of the actuator is connected to thefirst intermediate structure using any appropriate connection. Theopposing ends of the actuator 112 are connected to the two intermediatestructures operatively in parallel with the third actuator 113.Similarly, the first actuator is operatively in parallel with the gangedtogether second and third actuators. Further, it should be understoodthat each of the depicted connecting devices include at least one of aspring a damper, and/or a rigid connection.

In some embodiments, structure 114 may be the wheel assembly of avehicle while structure 115 may be a vehicle body. Correspondingly,actuator 111 may be an active suspension actuator, actuator 112 may be aroll assist actuator, and actuator 113 may be a ride height adjustmentactuator.

The embodiment shown in FIG. 7 is an example of a motion control unit120 that includes three actuators, 121, 122, and 123 arranged in aconfiguration similar to that described above in regards to FIG. 6.These actuators work cooperatively to control the relative motionbetween structure 124 and structure 125. Actuator 121 includes acompression volume 121 a, an extension volume 121 b, and a piston 121 cwhich is attached to piston rod 121 d. Actuator 122 includes acompression volume 122 a, an extension volume 122 b, and a piston 122 cthat is attached to piston rod 123 d. Actuator 123 includes acompression volume 123 a, an extension volume 123 b, and a piston 123 cthat is attached to piston rod 123 d. In this embodiment, eachcompression volume may be connected to an accumulator not shown) thatmay compensate for the volume of oil that is displaced by piston rodintrusion during operation. In the embodiment in FIG. 9, the extensionvolumes 121 b, 122 b, and 123 b are in fluid communication with a firstport of the hydraulic pump 127 by means of fluid flow paths 121 e, 122e, and 123 e respectively. Flow paths 121 e, 122 e, and 123 e mayinclude low pass hydraulic filters (and/or flow control devices) 121 f,122 f, and 123 f respectively.

Hydraulic actuators 122 and 123 are ganged together by structures 124 aand 125 a. Connecting devices 126 a, 126 b, 126 c, 126 d, and 126 econnect piston rod 121 d to structure 125, structure 125 to structure125 a, actuator 121 to structure 124, structure 124 to structure 124 a,and piston rod 123 d to structure 125 a. Connecting devices 126 a, 126b, 126 c, 126 d, and 126 e may be any appropriate combination of spring,damping and rigid elements.

In the depicted embodiment, low pass hydraulic filters 121 f, 122 f, and123 f are positioned along the associated flow paths between the pump127 and one or more of the compression and extension volumes of one ormore of the first, second, and third actuators 121, 122, and 123. Insome instances, low pass filters may be associated with both theextension and compression volumes of a specific actuator. The specificthreshold frequencies associated with the low pass filters may beassociated with one or more of these actuators to provide the desiredfrequency operation. Low pass filters 121 f, 122 f, and 123 f mayoperate in conjunction with at least the effects of compliance,dissipative component and fluid mass of flow paths 121 e, 122 e, and 123e to determine the frequency response of the actuators to pressure inputproduced by hydraulic pump 124 a. It is understood that the pump 127 maybe a hydraulic motor-pump that may function both as a pump and as ahydraulic motor.

Depending on the particular embodiment, an actuator, or other hydraulicdevice, may contain at least some of the components may be used as apart of as a low pass hydraulic filter. However, as explained above, insome embodiments, one or more additional components, such as forexample, a tuned orifice added to a flow path may interact with the flowpath to function as a low pass filter with certain desiredcharacteristics. Additionally, in other embodiments, a flow path may beconstructed and/or tuned to function as a low pass filter without theneed for any other components. Accordingly, various embodiments with ahydraulic low pass filter should be considered as including any of thesepossible alternatives, or other appropriate ways of constructing ahydraulic low pass filter, as the disclosure is not limited in thisfashion.

The embodiment of the motion control unit in FIG. 9 may be a part of anactive suspension system of a vehicle where structure 124 is a wheelassembly and structure 125 is a vehicle body. It is understood that, insome embodiments, the vehicle body is supported and its motioncontrolled by multiple motion control units, such as the motion controlunit 120 illustrated in FIG. 9. It is further understood that althoughthe actuators in FIG. 9 are shown to be double acting actuators, one ormore single acting actuators may be used instead of or in addition tothe actuators shown in FIG. 9 as the disclosure is not so limited.

In some embodiments of a vehicle where the motion control unit 120 isused, low pass filter 121 f may be eliminated and the actuator 121 maybe operated with a frequency response sufficient to control body andwheel motion at frequencies below 100 Hz. This may be achieved by usingan electric motor (not shown) that is operatively coupled to thehydraulic pump 124 a to produce pressure input to actuator 121 atfrequencies at or below 100 Hz. In such an embodiment, actuator 122 maybe used as a roll control actuator to control the roll motion of thevehicle body relative to the road on which the vehicle is traveling. Inthis embodiment, the low pass filter 122 f may attenuate all frequenciesabove a predetermined frequency, such as, for example, 3 Hz pressureinput from the pump and/or from movement of structure 124 relative tostructure 125.

In some embodiments, actuator 123 may be used to control the ride heightof a vehicle by controlling the nominal or equilibrium distance betweena vehicle body and wheel assembly corresponding to structures 124 and125. In such an embodiment, low pas filter 123 f may be used toattenuate all frequencies in the pressure delivered by pump 124 a abovea predetermined threshold frequency, such as, for example, 0.1 Hz.

While a particular applications and frequency ranges have been noted forthe actuators above, it should be understood that the various actuatorsand low pass filters may be configured to operate in any appropriatefrequency range and for any appropriate application including theapplications and frequency ranges noted above.

In addition to the above, each of the flow paths 121 e, 122 e, and 123e, depicted in FIG. 7 may include other or additional flow controldevices such as check valves, restrictions, fluid masses, flow limitingdevices, and/or shut off valves (not shown) which may be used inconjunction with, or instead of, the depicted hydraulic lowpass-filters. For example, flow path 123 e may include a shut off valve(not shown) which may be electrically, hydraulically, or pneumaticallyactivated to shut off the flow path and isolate actuator 123 frompressure input from pump 124 a. It is understood that the motion controlunit in FIG. 9 is shown with three actuators. However, any one of theactuators may be eliminated in some embodiments and/or additionalactuators may be added as the disclosure is not so limited.

In some embodiments, flow control devices may be designed and tunedaccording to the pressures and fluid flow in each system to achieve adesired level of flow mitigation. In one embodiment, a low passhydraulic filter 122 f, or other appropriate flow control device, may beused to effectively limit the range of operation of the associatedactuator to a threshold frequency appropriate for mitigating motionswith frequencies up to those experienced in a vehicle rolling orpitching (typically between 1 to 3 hz). For example, this flow controldevice may include a 1 mm diameter thin plate orifice. As pressure iscreated in pump 127, a force is generated in active suspension actuator,the first actuator 121. The pressure then causes the second actuator 122to extend against spring element 126 b. Before actuator 122 may exertforce between structure 125 and 124, fluid flow must occur throughelement 122 f. Therefore, by simply creating a tuned restriction (i.e.with a desired relationship between pressure drop and flowrate), whichmay correspond to the filter 122 f, the second actuator 122 may belimited to generating forces between structures 125 and 124 atfrequencies below a threshold frequency associated with body movementsor other appropriate movements. For example, the operation frequency ofthe second actuator may effectively be limited to less than or equal to5 Hz, 3 Hz, or any other appropriate frequency. Thus, any pressurefluctuations generated by the pump above this frequency threshold willcreate a force at actuator 121 but will be attenuated by the filter 122f and thus not generate a force at actuator 122. Again, this attenuationof high frequency pressure variations applied to actuator 122 may reduceboth the reflected inertia of the associated pump(s) and/or the powerrequired to pump enough oil to create forces with both actuator 121 and122 at higher frequencies.

FIG. 8 illustrates a motion control unit 130 which controls the relativemotion between the wheel assembly 131 of a vehicle and the vehicle body132. Active suspension actuator 133, is interposed between the vehiclebody 132 and the wheel assembly 131. The active suspension actuator maybe located to be operatively in parallel with a ride height actuator 134and suspension spring 135 that are arranged operatively in series withone another between the vehicle body and wheel assembly as well.Actuator 133 includes a compression volume 133 a and extension volume133 b that are separated by piston 133 c that is connected to thevehicle body by piston rod 133 d and an intervening top-mount 133 e.Hydraulic pump 136 is operatively connected to an electric motor (notshown) that is controlled to establish a desired pressure differentialat a pre-defined frequency across piston 133 c. In this embodiment, anaccumulator 137 is in fluid communication with compression volume 133 a.However, in some embodiments, an accumulator may be incorporated that isin fluid communication with the extension volume as an alternative, orin addition to accumulator 137. The extension volume 133 b is in fluidcommunication with the extension volume 134 b of the ride heightactuator 134 and one of the two ports of pump 136. The compressionvolume 134 a of actuator 134 is in fluid communication with anaccumulator 138, such as a gas charged accumulator. The exchange offluid to and from compression volume 134 a and extension volume 134 bmay be controlled by flow control devices 139 a and/or 139 brespectively, which as noted previously may be valve switches includingone or more of, check valves, shut-off valves, flow restrictions, or anyother appropriate component. The flow control valve 139 b, inconjunction with the flow characteristics of the flow channel 136 a, mayfunction as a low pass filter in order to attenuate pressurefluctuations produced by the pump 136 above a threshold frequency beforethey reach the extension volume 134 b of the ride height actuator.

Flow control device 139 a may be used to regulate the pressure incompression volume 134 a by connecting it to pressurized accumulator138. Pump 136 may be used to control the pressure differential acrosspiston 133 c of active suspension actuator 133 in order to controlmotion of the vehicle body 132 relative to the wheel assembly 131. Flowcontrol devices 139 a and 139 b may be used to control the pressureacross piston 134 c. Thus, the differential pressures across piston 133c and piston 134 c may be controlled to determine the ride height of thevehicle.

In the embodiment depicted in FIG. 8 actuator 134, as well as otheractuators in other embodiments described herein, are described andillustrated to support and adjust the position of a spring perch toaffect vehicle roll during turns and/or vehicle height. These springperches are typically shown as supporting and/or adjusting the positionof a suspension spring that is shown as a helical spring. However, theseactuators may also be used to apply a roll force by acting on avehicle's roll bar. One or more actuators in a motion control unit or asuspension control unit may be used to act on a spring perch or a rollbar individually or on both a spring perch and a roll barsimultaneously.

FIG. 9 shows a motion control unit 140 which includes two actuators. Anactive suspension actuator 141 is interposed between a vehicle body 142and a wheel assembly 143 operatively in a parallel configuration with aride height actuator 145. The ride height actuator may be located in anoperatively series arrangement with a suspension spring 146 locatedbetween the vehicle body and wheel assembly. In this embodiment, theride height actuator is a single-acting actuator. A pump 148 is in fluidcommunication with the associated pressurized volumes of the actuators.A flow control device 147 may be disposed between the pump and at leastone pressurized volume of actuator 145, which in the depictedembodiment, is a single acting actuator. The flow control device maywork in conjunction with the flow characteristics of flow channel 147 ato act as a low pass filter in order to mitigate pressure fluctuationsapplied to actuator 145 above a desired threshold frequency. It shouldbe noted that by choosing the proper characteristics of the flow controldevice 147, it may be used as a low-pass filter with an appropriatecutoff frequency, so the actuator 145 may be used as a spring perchcontrol actuator to function in an appropriate frequency range (forexample, in some embodiments, 3 Hz and below to mitigate vehicle rollforces, or 0.3 Hz and below to create ride height adjustments orcompensate for changes in vehicle weight) In some embodiments, actuator145, the flow control device 147, and flow channel 147 a characteristicsmay be selected to effectively use the actuator for roll control or rideheight adjustment. Though embodiments in which other frequencythresholds and/or applications are used are also contemplated.

The schematic in FIG. 10 illustrates another embodiment of an integratedmotion control unit 230 that includes an active suspension actuator 202and an auxiliary actuator 231 that work cooperatively to control therelative motion between a vehicle body 204 and wheel assembly 205. Inthis embodiment, the auxiliary actuator 231 may include a double actinghydraulic cylinder 232 with piston 233 and piston rod 233 a, which isattached to spring perch 218 a. The spring perch supports spring 218,which supports the vehicle body 204.

As in the previously described embodiments, the active suspensionactuator 202 is interposed between the wheel assembly 205 and thevehicle body 204 operatively in parallel with spring 218 and actuator231 which may be arranged operatively in series with one another.Typically the top of piston rod 208 may be attached to the vehicle bodyby a top mount (not shown). In the embodiment in FIG. 10, cylinder 232of the active suspension actuator may include a compression volume 234and extension volume 235.

In the depicted embodiment, the extension volume 210 of the activesuspension actuator 206 and the extension volume 234 of the cylinder 232of auxiliary actuator 231 may be in fluid communication through one ormore conduits such as conduit 236 a and conduit 237. The compressionvolume 209 of the active suspension actuator may be in fluidcommunication with the compression volume 234 of the auxiliary actuatorby means of one or more conduits such as conduits 234 b and 239. In someembodiments, a flow restriction, or other component or components, mayact as a low pass hydraulic filter along one or both of these flow pathsas illustrated by the flow restriction 238 which may be used to regulatethe flow of fluid through conduit 237. The restriction may be, forexample, an orifice, a manual valve, an electrically controlled valve, apressure controlled valve, or any other appropriate or convenientrestriction. Therefore, in some embodiments, the presence of flowrestriction 238 working with the flow characteristics of conduits 236 aand 237 may act as a low pass filter such that the hydraulic motor-pumpmay drive the active suspension actuator 202 as a fast response actuatorand auxiliary actuator 231 as an actuator with a slower response (i.e.the threshold frequency of the filter limits the operational frequenciesof the auxiliary actuator to a frequencies less than at least a maximumoperational frequency of the active suspension actuator). Again, such anarrangement may reduce the effective inertia of the system at higherfrequencies, while still allowing additional force to be applied atlower frequencies. The force amplification results from the increasedarea exposed in both pumps to the differential pressure generated bymotor-pump 211 at low frequencies, but limits the fluid flow through thepump at higher frequencies.

In some embodiments, the system of FIG. 10 may be configured for use ina typical sedan. In such an application, for example, the restingnominal pressure of the accumulator 212 may be approximately equal to400-800 psi and the diameter of the piston 207 may be equal toapproximately 30 mm-60 mm. Correspondingly, in some embodiments, thearea of piston 233 may range from approximately half to triple the areaof piston 207.

FIG. 11 shows an example of the performance of a suspension systemconstructed according to an embodiment similar to the system depicted inFIG. 12 where a vehicle has an integrated suspension unit at eachcorner. Graph 241 shows the lateral acceleration achieved by a typicalsedan while traveling on a slalom course at 40 mph. This particularsedan has a mass of 1900 kg, track width of 1.6 m, and a center ofgravity located at 0.56 m above the ground. In order to achieve fullbody control (holding the vehicle completely level in the turns) theforce required to mitigate vehicle roll on the front right wheel wascalculated based on the parameters of the vehicle and lateralaccelerations. In this embodiment of the system, the area of theauxiliary actuator piston was 80% of the area of the active suspensionsystem piston. The flow control device was modeled as a flat plateorifice with fluid flow properties tuned to give an approximate 2.5 Hzattenuation frequency of force generation from the auxiliary actuator.Line 245 shows the total force required from the entire activesuspension system to achieve ideal body control. Line 247 shows theelectrical power consumption required of a representative hydraulicpump, with typical electrical and hydraulic pump loses, working inconjunction with only actuator the active suspension actuator to exertthe entire force shown in line 245. The response of a system includingboth an active suspension actuator, a flow control device, and anauxiliary actuator, where graph 242 shows that the force 243 produced bythe auxiliary actuator supplements the force 244 produced by the activesuspension actuator. Although the total force generated by both systemsis the same in both magnitude and frequency, since the pump did not haveto generate as much pressure (it is now acting over a larger area) therequired power to perform this maneuver is greatly reduced. Graph 246shows the electrical power consumed by the electric motor (not shown) tooperate the hydraulic motor-pump in both cases. Specifically, the powerconsumption 247 when the active suspension actuator is acting alone isgreater than the power consumption 248 of a system where an activesuspension actuator and auxiliary actuator are being operatedcooperatively to control the force output.

FIG. 12 shows another embodiment of an integrated suspension unit 250with a first actuator 251 and a slower response second actuator 252interposed between a vehicle body 253 and a wheel assembly 254. A firstport of a pump 255 is in fluid communication with the extension volumes251 a, 252 a. The second port is in fluid communication with compressionvolumes 251 b and 552 b of the first and second actuators. Flow controldevices 256 a and 256 b disposed along the flow channels 257 a and/or257 b between the pump and extension and compression volumes of thesecond actuator, in conjunction with the flow channels they are in fluidcommunication with, may act as low pass filters to mitigate pressurefluctuations above a certain threshold frequency produced by pump 255.The threshold frequency selected for each low pass filter maybedetermined, at least in part, by the intended use of the actuator 252.As depicted in the figure, in some embodiments, the second actuator maybe located operatively in series with a spring or other connectingdevice.

FIG. 13 illustrates another embodiment of an integrated suspension unit260. In this embodiment, a first port of pump 255 may be in fluidcommunication with the extension volume 251 a of a first actuator andthe compression volume 252 b of a second actuator. Additionally, asecond port of the pump may be in fluid communication with thecompression volume 251 b of the first actuator and the extension volume252 a of the second actuator. Additionally, one of more flow controldevices 261 a and/or 261 b may be located between the pump and theextension and/or compression volumes of the second actuator to determinea frequency response of the second actuator 252 by attenuation ofpressure fluctuations, above a certain frequency threshold.

In the embodiment shown in FIG. 14, an integrated suspension unit 300may include an active suspension actuator 302, an auxiliary actuator301, and a height adjustment actuator 303. These three actuators maywork cooperatively to control the relative motion between the vehiclebody 304 and the wheel assembly 305 across a broad range of frequenciesas well as adjusting the ride-height of the vehicle. Additionally oralternatively the actuator 303 may be used to assist the auxiliaryactuator 301 in its function.

///The active suspension actuator 302 and auxiliary actuator 301 of thisembodiment may work cooperatively to control the motion of the vehiclebody relative to the wheel assembly. The ride height actuator 303 maywork in conjunction with the other two actuators to control ride heightand support vehicle weight under static conditions. For example, in someembodiments, the active suspension actuator 302 acts over a broad rangeof frequencies to mitigate road induced vertical motion imparted to thevehicle body as the vehicle travels over a road, typically 0-50 Hz. Theauxiliary actuator 301 may react more slowly, and acts through spring304 a to assist the active suspension actuator 302 by increasing theapplied force on the vehicle body 304 and typically operates infrequency ranges below 5 Hz. In some embodiments, the frequency responseof the active suspension actuator 302 may be equal to or greater than 50Hz, while the frequency response of the auxiliary actuator 301 may beequal to or less than 5 Hz.

In some embodiments, if a vehicle is traveling along a curve in theroad, one or more auxiliary actuators may increase the leveling forcethat an integrated suspension unit 300 may apply. For example, if theunit depicted in FIG. 14 is to apply a force in the upward direction,the pressure differentials produced by the pump 306 at frequencies belowa desired threshold may be applied to the piston 307 as well as piston330, increasing the applied force due to the increased effective pistonarea. However, the response of piston 330 to higher frequency changes inpressure, produced by the motor-pump above the threshold frequency,would be attenuated because flow control device 340 acts as a hydrauliclow pass filter as described above.

For the embodiment shown in FIG. 16, pistons 330 and 315 are constrainedto move together. Therefore, if vehicle ride-height is changed to a newneutral position, the flow control device 341 may be closed to lockpiston 315 in that new position. However, if the auxiliary actuator 301is engaged to, for example increase roll hold capacity, an associatedflow control device 341 disposed between a pressurized accumulator 322and the compression volume 314 of the height adjustment actuator 303 maythen be at least partially opened to allow piston 330 to move up ordown.

The embodiment illustrated in FIG. 15, is similar to the embodimentdescribed above in regards to FIG. 14 and the same reference numbers areused to indicate corresponding elements. In this embodiment, flowcontrol device 342 and flow path 342 a, which connect a port of pump 306to the compression volume 334, may be used to mitigate pressurefluctuations above a certain frequency threshold, such as for example 3Hz, before they reach compression volume 334. Flow control device 343may be used in a similar manner to mitigate pressure fluctuations abovea certain preset frequency threshold produced by pump 306 from reachingthe extension volume 330. However, in some embodiments, either flowcontrol device 342 or 343 may be eliminated. It should be noted that, inthis embodiment, the fluid communication between the extension andcompression volumes of actuators 301 and 302 are inverted relative tothe embodiment in FIG. 14.

FIG. 16 illustrates one embodiment of an integrated motion control unit400 which includes an active suspension actuator 402, an auxiliaryactuator 421, and a height adjustment actuator 422. These threeactuators may work cooperatively to control the relative motion betweenthe vehicle body 404 and wheel assembly 405, as well as the ride-heightof the vehicle.

In the embodiment depicted in FIG. 16, accumulator 424 may be in fluidcommunication with, and control a pressure in, the compression volume414 of the height adjustment actuator 422. The accumulator 424 mayinclude four chambers: (1) hydraulic fluid filled chamber 424 a, that isin selective fluid communication with hydraulic motor-pump 411 andextension volume 410 of the active suspension actuator through flowcontrol device 425, (2) hydraulic fluid filled chamber 424 b that is inselective fluid communication with compression volume 414 of the heightadjustment actuator through flow control device 426, (3) gas filledchamber 424 c and (4) gas filled chamber 424 d.

In the embodiment of FIG. 16, accumulator 424 is substantiallycylindrical in shape with cylindrical segment 424 e and end-caps 424 fand 424 g. Internal cylinder 424 h is attached at one end to end-cap 424f. The accumulator 424 may also include an annular piston 427 a andpiston 427 b formed in a top-hat configuration. The top-hat piston 427 bcomprises an axially protruding portion 427 c that has a smallerdiameter than a second portion 427 d that extends radially outward froman end of the axially protruding portion. The axially protruding portionis slidably received in the open end of internal cylinder 424 h. Thechambers 424 a, 424 b, 424 c and 424 d may be mutually sealed to preventexchange of gas and/or fluid between the chambers using any convenientdevice or method including, for example o-rings 427 e.

In the embodiment of FIG. 16, fluid pressure in chamber 424 a may becontrolled by operating motor-pump 411 and positioning a flow controldevice 425 to allow flow into or out of the chamber 424 a. Duringoperation, the pressure in chamber 424 b may be increased by reducingthe volume of fluid in chamber 424 a. Flow of fluid out of chamber 424 awould cause piston 427 b to move further into internal cylinder 424 hthus increasing the pressure in chamber 424 c. By positioning valve 426to allow flow between volume 424 b and volume 414, the pressure incompression volume 414 may be increased. By reversing the motorsoperation, and increasing the volume of fluid in chamber 424 a, thepressure in compression volume 414 may be decreased. In the embodimentin FIG. 16, the force on piston 427 b due to the pressure in gas filledchamber 424 d may be designed to be greater that the net force on piston427 b due to the gas pressure in chamber 424 c.

In the embodiment shown in FIG. 16, the chamber 424 a of the accumulatoris in selective fluid communication with extension volumes of actuators402 and 421 through flow control device 425. Thus, the accumulator 424may be used to control the pressure in the compression volume 414 of thecorresponding height adjustment actuator 422.

FIG. 17 illustrates an embodiment of an integrated suspension unit 450with an active suspension actuator 452 and height adjustment actuator453. Piston rod 453 a is attached to spring perch 458 a, which supportsspring 459. In this embodiment, compression volume 453 b may bepressurized by accumulator 460. Accumulator 460 may be partially filledwith air 460 a which is separated from hydraulic fluid 460 b by meansof, for example, piston 460 c. Valve 461 may be used to add pressurizedair to the accumulator.

In this embodiment, a hydraulic motor 462 may operate as a power-takeoffunit to drive an air compressor 462 b. The air compressor 462 b may beused to increase the pressure in the accumulator to drive more fluidinto actuator 453 in order to raise a vehicle 470 associated with theactuators. Conversely, the vehicle may be lowered by allowing air toleave accumulator 460, thus allowing fluid to flow out of compressionvolume 453 b. In some embodiments, flow control device 477 may be usedto control exchange of fluid into and/or out of the compression volume453 b. Flow control device 477 may be used to control fluid exchangebetween hydraulic motor-pump 462 a and hydraulic motor 462.

FIG. 18 illustrates another embodiment of an integrated suspension unit500 with an active suspension actuator 502 and ride height actuator 453.The ride height actuator piston rod 453 a is attached to spring perch458 a, which supports spring 459. In this embodiment, compression volume453 b may be pressurized by accumulator 502. Accumulator 502 may bepartially filled with gas 502 a which is separated from hydraulic fluid502 b by means of, for example, diaphragm 502 c. Alternatively, a piston(not shown) may be used instead of the diaphragm to separate thepressurized gas from the hydraulic fluid. Valve 502 d may be used to addgas to the accumulator. In the depicted embodiment, a hydraulic motor513 may operate as a power take-off unit to drive a hydraulic pump 504.Hydraulic pump 504 may be used to control fluid flow between accumulator502 and compression volume 543 b in order to raise or lower the vehicle.

In the above embodiments, the motion control units include actuatorsshown as distinct hydraulic actuators. In some embodiments, distinctactuators may be used in application such as when the active suspensionactuator and the vehicle suspension spring are not co-located. However,in other embodiments, it may be desirable to consolidate two or moreactuators into a single apparatus.

FIG. 19 illustrates one possible an embodiment of a consolidatedapparatus that includes two actuators. In the depicted embodiment, theprimary actuator 505 includes a pressure tube 505 a that encloses avolume 506 that is at least partially filled with a hydraulic fluid. Atleast a portion of the exterior surface 505 b of actuator 505 iscylindrical. The volume 506 is divided into a compression volume 506 aand an extension volume 506 b by piston 507. The piston is slidablyreceived in the pressure tube. The extension volume 506 b is on the sideof piston 507 that is attached to piston rod 507 a that extends out fromthe pressure tube. Compression volume 506 a is on the side of the pistonopposite the side that is attached to the piston rod. The primaryactuator 505 may be disposed between a wheel assembly 512 and a topmount 513 of a vehicle in order to control the relative motion betweenthe vehicle body and the ground, though the actuator may be used tocontrol the relative movement of other structures as well.

In the embodiment illustrated in FIG. 19, hydraulic motor-pump 508 is influid communication with the compression volume 506 a of the primaryactuator through conduits 508 a and 508 b and is in fluid communicationwith extension volume 506 b by through conduit 509, conduit 510, andopening 511 formed in an internal tube wall of the primary actuator. Thehydraulic motor-pump 508 controls the force applied by the actuatorbetween the vehicle body and the ground by pumping fluid between thecompression volume and the extension volume. The pressures in the twovolumes may be directly controlled by appropriately controlling theoperation of the motor pump. As described above, a motor-pump is ahydraulic device that may be used as both a pump and/or hydraulic motor.In some embodiments, an accumulator 514, or other appropriate structuresuch as a compressible medium or bladder capable of accommodatingfluctuations in fluid volume, is in fluid communication with at leastone of the extension and compression volumes. In the depictedembodiment, the accumulator, or other appropriate structure, is sized toat least accommodate the fluid volume displaced by introduction of thepiston rod into the pressure tube by supplying fluid to or receivingfluid in volume 506.

Accumulator 514 may include a compressible medium 514 a, such as forexample nitrogen gas or air, that may be separated from the hydraulicfluid by a piston 514 b or other separation device. The hydraulicmotor-pump 507 is operatively coupled to an electric motor (not shown),which may be operated as a motor or a generator, i.e. the electric motormay be operated to drive the associated hydraulic motor-pump or thehydraulic motor-pump may drive the electric motor depending on the modeof operation. For example, a primary actuator 501 may be controlled by acontroller (not shown) to operate in any one or more of its four forcevelocity quadrants.

In the embodiment of FIG. 19, an integrated auxiliary actuator piston515 may be annular in shape with a central opening that is slidablyreceived over at least a portion of the cylindrical exterior surface 501b of the primary actuator housing. Thus, the auxiliary actuator pistonmay extend radially around and along at least a portion of the axiallength of the primary actuator's housing. In other embodiments theauxiliary actuator piston may be of any other convenient shape that mayor may not be annular. An additional volume of fluid may be contained inthe volume 516 located between the inner surface of annular auxiliaryactuator piston 515 and cylindrical surface 501 b of the primaryactuator. This volume may be separated into two auxiliary volumes 516 aand 516 b located on either side of a protrusion 517 extending radiallyoutward from the primary actuator. This protrusion may either beattached to, or integrally formed with, the cylindrical surface 501 b ofthe primary actuator.

The interface between the auxiliary actuator piston 515 and the externalsurface 501 b of the primary actuator may be sealed by seals 518 a and518 b. These seals may correspond to any appropriate sliding sealedinterface including, for example, O-ring seals. Correspondingly, theprotrusion 517 of the primary actuator may be sealed against an interiorsurface of the auxiliary actuator piston by a seal 518 c disposed therebetween. For example, an O-ring seal may be located between the innersurface of auxiliary actuator piston 515 and an outermost surface of theprotrusion. With seals 518 a, 518 b, and 518 c in place the auxiliaryvolumes 516 a and 516 b may be pressurized to different pressures.Volume 516 a may be in selective fluid communication with an accumulator514 and compression volume 506 a of the primary actuator throughconduits 508 b, 508 c, and 508 d, while volume 516 b is in fluidcommunication with the extension volume of the primary actuator throughan internal volume 510 of the primary actuator, such as the outertubular space in a double tube arrangement, through openings 511 and 519formed in the inner and outer tubular walls of the primary actuator.Valves, such as for example diverter valves, may be used to control theflow in one or more of the conduits of the depicted apparatus. Forexample, a valve 520 may be an on/off solenoid valve, variable valve, orany other valve that may be used to isolate volume segment 516 a fromthe rest of the hydraulic circuit including, for example, theaccumulator, the hydraulic motor-pump, and compression volume 503. Theinteractions of these various components to control actuation of theauxiliary actuator is further described below.

In some applications, an auxiliary actuator piston 515 may be used as aspring perch for a spring 521, which may be a helical spring or anyother convenient spring that is interposed between the wheel assembly512 and a vehicle body (not shown). Alternatively or additionally, theauxiliary actuator piston 515 may be attached to a point on a roll-baror stabilizer bar (not shown). The auxiliary actuator piston 515 may beused, individually or in concert with one or more other auxiliaryactuator pistons and/or one or more other primary actuators, to adjustvehicle ride height, ground clearance, or degree of vehicle roll.

During operation of the embodiment of an integrated actuator depicted inFIG. 19, a primary actuator 505 may be a fully active actuator, asemi-active damper, and/or a passive damper. Additionally, the depictedaccumulator 514 may be charged to any appropriate pressure. Under thesecircumstances, if the hydraulic motor-pump is not operating and thesystem reaches equilibrium, the pressures in the compression volume 503and extension volume 504 will eventually equal the charge pressure ofthe accumulator. Therefore, at equilibrium the net force on piston 505will be equal to the pressure in the compression volume multiplied bythe cross-sectional area of the piston rod 506. Therefore, if, forexample, the charge pressure of the accumulator is 30 bar, the primaryactuator system is in equilibrium, and the diameter of the piston rod is15 mm, a force of approximately 530 N force will be applied to the topmount along the axis of the piston rod.

When it is desired to prevent actuation of the auxiliary piston, flowcontrol device 520 is may be configured to seal auxiliary volume 516 a.When flow control device 520 is so configured, the motion of theauxiliary actuator piston 515 is constrained due to the fluid trapped inauxiliary volume 516 a being effectively incompressible while theleakage through seals 518 a, 518 b, and 518 c is minimal. However, it isnoted that at least some small amount of movement may occur due to allsystems typically have some amount of compliance and/or leakage.

When it is desired to actuate the auxiliary piston, the flow controldevice 520 may be at least partially opened. Once this occurs, thehydraulic motor-pump 507 may be used to apply a net force to theauxiliary actuator piston by establishing a differential pressurebetween the auxiliary volumes 516 a and 516 b located on opposing sidesof the protrusion extending outwards from the primary actuator housingmay correspond to auxiliary extension and compression volumesrespectively. In the embodiment shown in FIG. 21, the pressure in 516 amay be reduced or increased relative to the pressure in 516 b byoperating the hydraulic motor-pump 507 to reduce or increase thepressure in the auxiliary extension volume relative to the pressure inthe auxiliary compression volume respectively. In the embodiment of FIG.21, the net force in the axial direction applied on the auxiliaryactuator piston 515 due to internal pressure is the pressure in theauxiliary extension volume multiplied by an area of surface 516 c of theauxiliary piston within the auxiliary extension volume minus thepressure in the auxiliary compression volume multiplied by an area ofsurface 516 d of the auxiliary piston within the auxiliary compressionvolume.

The shape of the of the auxiliary actuator piston 515 may be anyconvenient shape, whether annular or not, that may effectively engagethe primary actuator and one or more spring elements of the suspensionsystem of a vehicle. The areas 516 c and 516 d noted above correspond tothe areas that are effectively acted upon by the pressure of thehydraulic fluid in volume elements 516 a and 516 b, respectively, duringactuation of the auxiliary actuator. The areas 516 c and 516 d may be ofequal size or they may be different in size relative to each other asthe disclosure is not so limited. The relative size of these elementswill determine the relative pressures need in auxiliary volumes 516 aand 516 b in order to exert a desired force in a desired direction on aparticular spring element. Accordingly, vehicle height may be adjustedby applying the resulting net force to the bottom of spring 521.Alternatively or additionally, the auxiliary actuator piston may be usedto apply a force between the wheel assembly and the vehicle body toaugment a force applied by the primary actuator. Alternatively oradditionally, the auxiliary actuator piston may be used to apply a forceto a roll-bar of a vehicle in a manner that alters the torque in theroll-bar.

In some embodiments, the auxiliary actuator piston 515 may be raised,relative to wheel assembly 512, through the use of a flow control device520. In the depicted embodiment, flow control device 520 is positionedand configured to selectively establish fluid communication between pump507 and auxiliary volume 516 a. When fluid communication is established,the pump may pump fluid into auxiliary volume 516 a, corresponding to anextension volume, to raise the actuator. Alternatively, auxiliaryactuator piston 515 may be lowered, relative to wheel assembly 512, byreducing the pressure in auxiliary volume 516 a, the auxiliary extensionvolume, relative to the pressure in auxiliary volume 516 b, theauxiliary compression volume. Accordingly, the auxiliary actuatordepicted in FIG. 19, is a dual acting piston. Further, when the areas516 c and 516 d are equivalent, then the actuator piston may functionequivalently to a dual acting piston with a through rod. Additionally,in some embodiments, the flow control device 520, in conjunction withthe flow passages it is associated with, may also function as a low passfilter between the auxiliary volume 516 a and the pump 507. Accordingly,in this manner, the frequency response of the auxiliary actuator 515 maybe different than the frequency response of the primary actuator 501 ina similar fashion to the integrated actuator systems described above.

In some embodiments, it may be desirable to increase the force of anauxiliary actuator piston without increasing the overall cross sectionalarea of the device. Accordingly, FIG. 20 illustrates an embodiment withan auxiliary actuator piston 550 that includes at least two auxiliaryvolumes 551 and 552 formed by multiple protrusions extending out fromthe primary actuator housing and similar protrusions extending inwardsfrom the auxiliary actuator housing to form multiple auxiliarycompression and extension volumes 551 and 552 which may operate in amanner similar to that described above. Specifically, in the depictedembodiment, auxiliary volume portions 551 a and 552 a, corresponding toextension volumes, are in fluid communication with each other andauxiliary volume portions 551 b and 552 b, corresponding to compressionvolumes, are in fluid communication with each other. Accordingly,surface areas associated with these auxiliary volumes may increase theeffective surface area the pressures are applied to without increasingthe overall cross section of the auxiliary actuator piston. For example,in the depicted embodiment, the net force applied to the auxiliaryactuator piston 550 is equal to the pressure of the fluid in auxiliaryvolume 551 a multiplied by the area 553 a plus pressure of the fluid inauxiliary volume 552 a multiplied by the area 554 a minus pressure ofthe fluid in auxiliary volume 551 b multiplied by the area 553 b minuspressure of the fluid in auxiliary volume 552 b multiplied by the area554 b. In other words, the combined areas of the multiple extensionauxiliary volumes multiplied by the corresponding pressures in thoseextension volumes minus the areas of the multiple auxiliary compressionvolumes multiplied by the corresponding pressures in those compressionvolumes provides the resulting force applied to the auxiliary actuatorpiston. By using one, or a plurality of, protrusions extending inwardsfrom an inner surface of the auxiliary actuator piston, may form a twoor more corresponding pairs of extension and compression auxiliaryvolumes, along with and the corresponding areas, along a length of aprimary actuator. These areas associated with the plurality of auxiliaryvolumes may increase the effective area on which the net pressure isapplied to the auxiliary actuator piston without increasing the outsidediameter of the auxiliary actuator piston.

FIG. 21 illustrates another embodiment with a primary actuator 560 andauxiliary actuator piston 561. Auxiliary actuator piston 561 has aninner cylindrical opening that slidably receives at least a portion ofcylindrical surface 565 of the primary actuator. An auxiliary volume 562may be formed by the outer surface 561 b of actuator 561 which is sealedagainst the inner surface 563 a of axially extending cylinder 563 andthe annular protrusions 563 b and 563 c that extend radially inwardlyfrom surface 563 a of the cylinder 563 towards the outer surface 561 aof actuator 561. Cylinder 563 may be attached to the primary actuator560 or otherwise fixed relative to the wheel assembly 564. Volume 562 isdivided into auxiliary volume portions 562 a and 562 b by radiallyoutwardly extending protrusion 561 b to form the extension andcompression volumes respectively. These auxiliary volume portions may besealed relative to each other and the exterior environment by seals 566a, 566 b and 566 c, which may be for example O-ring seals. Auxiliaryvolume portion 562 a may be in fluid communication with a first port ofa hydraulic motor pump 569 and the auxiliary volume portion 562 b may bein fluid communication with a second portion of the pump. In someembodiments, the fluid communication between the second port of the pumpand auxiliary volume portion 562 is through a valve 568 or other flowcontrol device.

In the embodiment in FIG. 21, the net force applied to actuator 561 dueto the pressure of the hydraulic fluid in auxiliary volume portions 562a and 562 b is equal to the pressure of the hydraulic fluid in thesevolumes multiplied by the areas 561 c and 561 d of these volumesrespectively. The pressures in auxiliary volume portions 562 a and 562 bmay be controlled during operation in a similar fashion to controllingthe pressures in the auxiliary volumes described in the embodiment ofFIG. 19.

By using the embodiment of FIG. 23, vehicle height may be adjusted byapplying the resulting net force to the bottom of spring 567.Alternatively or additionally, the auxiliary actuator may be used toapply a force between the wheel assembly and the vehicle body to augmentthe force applied by the primary actuator. Alternatively oradditionally, the auxiliary actuator piston may be used to apply a forceto a roll-bar of a vehicle in a manner that alters the torque in theroll-bar.

In some embodiments the auxiliary actuator piston 561 may be raised,relative to a wheel assembly 564, by at least partially opening a valvecontrolled by fluid control device 568 and pumping fluid into auxiliaryvolume portion 562 b. Alternatively, in some embodiments, the auxiliaryactuator piston 561 may be lowered, relative to the wheel assembly 564,by at least partially opening valve 568 and increasing the pressure involume 562 a to a pressure sufficiently higher than the pressure involume element 562 b by using hydraulic motor pump 569.

Again, a shape of the of the auxiliary actuator piston 561 may be anyconvenient shape, whether annular or not, that may effectively engagethe primary actuator 560 and one or more spring elements of thesuspension system of a vehicle. The areas 561 c and 561 d associatedwith the auxiliary volume portions represent the areas that areeffectively acted upon by the pressure of the hydraulic fluid in theauxiliary volume portions 562 a and 562 b, respectively. The areas 561 cand 561 d may be of equal size or they may be different as thedisclosure is not so limited. Additionally, the relative size of theseelements may be used to determine the relative pressures needed inauxiliary volume portions 562 a and 562 b in order to exert a desiredforce in a desired direction on a particular spring element.

FIG. 22 illustrates another embodiment with a primary actuator 570 andauxiliary actuator piston 571. The integrated auxiliary actuator piston571 may be annular in shape with a central opening that slidablyreceives at least a portion of a cylindrical exterior surface 571 b ofthe primary actuator. Auxiliary volume 572 is formed by the innersurface 571 a of the annular auxiliary actuator piston 571, thecylindrical exterior surface 571 b of the primary actuator, and aprotrusion 573 extending radially outward from the exterior surface ofthe primary actuator. The protrusion may either be attached to, orintegrally formed with, the cylindrical surface 571 b. Similar to theabove embodiments, an interface between the auxiliary actuator piston574 and surface 571 b may be sealed by seal 575, which may be forexample an O-ring seal. A radially outermost edge of protrusion 573 maysimilarly be sealed by seal 576, which may be for example an O-ringseal, against the inner surface of auxiliary actuator piston 571.

In some embodiments, a hydraulic motor-pump 580 is in fluidcommunication with an extension volume 579 a and compression volume 579b of the primary actuator. The hydraulic motor pump and/or anaccumulator 581 may also be in fluid communication with the auxiliaryvolume 572 through a flow control device 578. Thus, the auxiliaryactuator piston 574 may be raised, relative to wheel assembly 577, byconfiguring the fluid control device 578 to provide fluid communicationbetween the hydraulic motor pump and/or the accumulator. This may resultin fluid being pumped into the auxiliary volume 572. Alternatively, insome embodiments, auxiliary actuator piston integrated motion controlunit 574 may be lowered, relative to wheel assembly 577, by positioningfluid control device 578 to provide fluid communication between volume572 and the hydraulic motor pump and/or the accumulator. The pressure involume 579 may then be reduced sufficiently to lower the auxiliaryactuator relative to the wheel assembly 577.

FIG. 23 illustrates another embodiment with a primary actuator 580 andauxiliary actuator piston 581. Auxiliary actuator piston 581 has aninner cylindrical opening that slidably receives at least a portion ofcylindrical surface 582 of the primary actuator. The primary actuatoralso includes an outer cylinder 586 in addition to the primary cylinderhousing the primary actuator that is sized and shaped to slidablyreceive at least a portion of the auxiliary actuator piston. Anauxiliary volume 583 is formed by the outer surface 584 of auxiliaryactuator piston 581, the inner surface 585 of axially extending cylinder586, a protrusion 587 that extends radially inwardly from a surface 585of the outer cylinder 586 of the primary actuator towards the outersurface 588 of the auxiliary actuator piston 581. A correspondingprotrusion 589 extends radially outwardly from the outer surface 584 ofthe auxiliary actuator piston towards an inner surface of the outercylinder of the primary actuator. Auxiliary volume 583 may be sealed byseals 592 and 593, which may be for example O-ring seals. The outercylinder 586 may be attached to the primary actuator 580, or otherwisefixed relative, to the wheel assembly 590 in any appropriate fashion.

In the embodiment depicted in FIG. 23, the force applied to theauxiliary actuator piston 581 due to the pressure of the hydraulic fluidin auxiliary volume 583 is equal to the pressure of the hydraulic fluidin the volume multiplied by the corresponding effective area 591. Thepressure in the auxiliary volume 583 may be controlled during operationin a fashion similar to that described above in relation to FIG. 22.

By using the embodiment of FIG. 23, vehicle height may be adjusted byapplying the resulting net force to the bottom of spring 594.Alternatively, or additionally, the auxiliary actuator may be used toapply a force between the wheel assembly and the vehicle body to augmentthe force applied by the primary actuator. Alternatively oradditionally, the auxiliary actuator piston may be used to apply a forceto a roll-bar of a vehicle in a manner that alters the torque in theroll-bar.

In some embodiments the auxiliary actuator piston 581 may be raised,relative to a wheel assembly 590, by configuring flow control device 595to permit at least some fluid communication to pump fluid into volume583 using a hydraulic motor-pump 598. Alternatively, in someembodiments, auxiliary actuator piston 581 may be lowered, relative tothe wheel assembly 590, by configuring the flow control device 595 toestablish fluid communication between pump 598 and volume 583.

FIG. 24 illustrates an embodiment of an integrated actuator 600 thatincludes a primary (active suspension) actuator 601 and an auxiliaryactuator 602. The primary actuator 601 includes a hydraulic motor-pump603 that may be attached to a damper housing 604. U.S. Pat. No.9,035,477, entitled “Integrated energy generating damper,” describes anactive suspension actuator where the motor-pump is attached to thedamper housing. The description of the construction and operation ofsuch an active suspension actuator is incorporated herein by referencein its entirety. The hydraulic motor-pump 603 is in fluid communicationwith the compression volume 601 a by means of port 601 b and withextension volume 601 c through port 601 d.

In the depicted embodiment, the auxiliary actuator 602 includes ahydraulically adjustable spring perch 605 that supports helicalsuspension spring 606. Spring 606 supports vehicle body 607. The pistonrod 601 e of the primary actuator is connected to the vehicle body 607by an intervening top mount 608. The auxiliary actuator 602 alsoincludes an internal volume 602 a that is in selective fluidcommunication with an accumulator 609. The fluid communication betweenthe volume 602 a and the accumulator 609 is controlled by a flow controldevice 610. During operation, the flow control device 610 may be used topressurize volume 602 a such that a force is applied by the auxiliaryactuator to the bottom of spring 606. The primary actuator 601 may thenbe used to raise and/or lower the vehicle by providing any force thatmay be required by controlling the differential pressure between volumes601 c and 601 a.

When the flow control device 610 is positioned to allow fluid exchangebetween volume 602 a and the accumulator, the pressures in these volumesmay become equilibrated over time. In some embodiments, by prechargingthe accumulator to a predetermined set pressure, the actuator maysupport the associated portion of the vehicle weight that is applied tospring 606. In some embodiments or under certain environmentalconditions, the set pressure may be within a range of ±10% of thepressure required to support the applied weight. In some embodiments orunder certain environmental conditions, the set pressure may be within arange of ±20% of the required pressure. It should be understood thatother precharge pressures both greater and less than the above notedrange are also contemplated as the disclosure is not so limited.

FIG. 25 illustrates an embodiment of an integrated actuator 620 thatincludes a primary actuator 601 and auxiliary actuator 621. An interiorvolume 621 a of the auxiliary actuator may be in fluid communicationwith an accumulator 609. However, fluid connection to volume 621 a isfixed relative to primary actuator 601 and does not move with actuator621. FIG. 26 illustrates yet another embodiment of an integratedactuator 630 that includes a primary actuator 601 and an auxiliaryactuator 631. The auxiliary actuator 631 includes an internal volume 631a that is in fluid communication with the compression volume 601 a ofthe primary actuator and a separate internal volume 631 b that is influid communication with the extension volume 601 c of the primaryactuator.

In this embodiment, the differential pressure produced by an associatedhydraulic motor-pump 603 is applied to both actuators. The net forceapplied by the integrated actuator on the vehicle body is equal becauseof the forces applied by the piston rod 601 e and the adjustable perch605. The force applied by piston rod 601 e is equal to the pressure inthe compression volume 601 a multiplied by the circular area 601 f ofpiston 601 g minus the pressure in extension volume 601 c multiplied bythe annular area 601 h of the piston 601 g. The net force applied by theadjustable perch 605 is equal to the pressure in volume 631 a multipliedby the area 632 a minus the pressure in volume 631 b multiplied by area632 b plus the pressure in volume 631 c multiplied by area 632 c.

The pressure in volume 631 c may be determined by the pressure inaccumulator 609 that is in fluid communication with volume 631 a andaccumulator 609 is controlled by flow control device 610. It should benoted that when the motor-pump 603 is not producing pressure, forexample when it is turned off, the pressures in volumes 601 a, 601 c,631 b and 631 b will equilibrate.

FIG. 27 illustrates still another embodiment of an integrated actuator640 that includes primary actuator 601 and auxiliary actuator 641. Inthis embodiment, the pressure in an accumulator is provided to auxiliaryvolume 642 of an auxiliary actuator piston where it is applied to acorresponding area 643. The volumes 601 c and 601 a are in fluidcommunication with volumes 644 a and 644 b respectively.

The embodiment in FIG. 28 illustrates another embodiment of anintegrated actuator 650 that is similar to actuator 630 in FIG. 28.However, in the integrated actuator 650, the accumulator is entirelycontained in annular volume 651 that is a part of auxiliary actuator652. In addition, in actuator 650, the flow control device 653 is usedto control the flow path between the compression volume 601 a andannular volume 654. The flow control device 653 may be closed tohydraulically seal volume 654 and lock actuator 652 in place relative toprimary actuator 601.

While the present teachings have been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present teachings encompass various alternatives, modifications, andequivalents, as will be appreciated by those of skill in the art.Accordingly, the foregoing description and drawings are by way ofexample only.

1. An active suspension unit of a motor vehicle, comprising: a firstactive suspension actuator with an internal volume and a first pistonthat is slidably received in the internal volume and travels along afirst axis, wherein the first actuator is interposed between a vehiclebody and a wheel assembly; a second actuator with an internal volumecontaining hydraulic fluid and a piston with a second axis of travel,wherein a pressure of the hydraulic fluid induces a force on the pistonalong the second axis of travel, wherein the second actuator isinterposed between the vehicle body and the wheel assembly; a firstpressure source with at least a first port that is in fluidcommunication with the internal volume of the first actuator; and asecond pressure source with at least a first port that is in fluidcommunication with the internal volume of the second actuator; whereinthe two actuators are controlled to cooperatively apply a net force onthe vehicle body and the wheel assembly.
 2. The active suspension unitof claim 1, wherein the first axis and the second axis are operativelyin parallel.
 3. The active suspension unit of claim 1, wherein the firstpressure source is a first hydraulic pump.
 4. The active suspension unitof claim 3, wherein the second pressure source is a second hydraulicpump.
 5. The active suspension unit of claim 4, wherein the firsthydraulic pump and the second hydraulic pump are the same device.
 6. Theactive suspension unit of claim 5, wherein the first actuator has afaster response than the second actuator.
 7. The active suspension unitof claim 4, wherein at least one of the first hydraulic pump and thesecond hydraulic pump is a hydraulic motor-pump. 8-31. (canceled)
 32. Anintegrated motion control unit, comprising: a first actuator thatincludes a housing with an internal volume separated into a compressionvolume and an extension volume by a double-acting piston and a pistonrod attached to the piston; a hydraulic pump that has a first port thatis in fluid communication with the extension volume, and a second portthat is in fluid communication with the compression volume; and a secondactuator that includes a first volume and a second volume and a doubleacting piston with a first surface acted on by the fluid in the firstvolume and a second surface acted on by the fluid in the second volume,wherein the first volume is in fluid communication with the first portof the hydraulic pump and the second volume is in fluid communicationwith the second port of the hydraulic pump; wherein the first actuatorand the second actuator are operatively in parallel to each other, andinterposed between a first and a second structure, and wherein the firstactuator has a faster response than the second actuator.
 33. Theintegrated motion control unit of claim 32, further comprising at leastone low pass hydraulic filter located along a flow path between thehydraulic pump and the second actuator.
 34. The integrated motioncontrol unit of claim 32, wherein the first structure is a vehicle bodyof a vehicle and the second structure is a wheel assembly of thevehicle.
 35. The integrated motion control unit of claim 33, furthercomprising a spring that is operatively in parallel with the firstactuator and operatively in series with the second actuator.
 36. Theintegrated motion control unit of claim 33, wherein the first actuatorhas a bandwidth extending to an upper limit of at least 10 Hz and thesecond actuator has a bandwidth extending to an upper limit of no morethan 3 Hz.
 37. The integrated motion control unit of claim 36, whereinthe first actuator has a bandwidth extending to an upper limit of atleast 20 Hz and the second actuator has a bandwidth extending to anupper limit of no more than 3 Hz.
 38. The integrated motion control unitof claim 33, further comprising a third actuator that includes a firstvolume and a second volume and a double-acting piston with a firstsurface acted on by the fluid in the first volume and a second surfaceacted on by the fluid in the second volume, wherein the first volume isin fluid communication with the first port of the hydraulic pump and thesecond volume is in fluid communication with the second port of thehydraulic pump, and herein the third actuator has a slower response thanthe second actuator.
 39. The integrated motion control unit of claim 38,wherein the third actuator has a bandwidth extending to an upper limitof no more than 0.5 Hz.
 40. The integrated motion control unit of claim36, wherein the first actuator has a bandwidth up to at least 20 Hz andthe second actuator has a band width up to no more than 3 Hz.
 41. Theintegrated motion control unit of claim 32, wherein the hydraulic pumpis a hydraulic motor-pump.
 42. A method of controlling relative motionbetween a first structure and a second structure by applying a net forceon the two structures, the method comprising: driving a hydraulic pumpwith an electric motor operatively coupled to the hydraulic pump;supplying pressurized hydraulic fluid to a volume in a first actuator,wherein the first actuator is interposed between the first and thesecond structures; supplying pressurized hydraulic fluid to a volume ina second actuator, wherein the second actuator is interposed between thefirst and the second structures and arranged operatively in a parallelarrangement with the first actuator; wherein the total Effective ForceArea of the first actuator and the second actuator in at least one ofthe compression direction and the extension direction is a function ofthe frequency of pressure produced by the hydraulic pump.
 43. The methodof claim 42, further comprising using a hydraulic low pass filterlocated in a flow path between a port of the hydraulic pump and at leastone of the compression volume and the extension volume of the secondactuator in order to reduce the Effective Force Area of the secondactuator above a threshold frequency.
 44. The method of claim 43,wherein the threshold frequency is 3 Hz.
 45. The method of claim 43,wherein the threshold frequency is 0.1 Hz.
 46. The method of claim 42,wherein the hydraulic pump is a hydraulic motor-pump. 47-69. (canceled)